Internet
Web Browsing
OffByOne Web Browser 3.5a [409k] + "May be the world's smallest and fastest Web Browser with full HTML 3.2 support.
Lynx for Win32 v. 2-8-3 [714k] {S}+ Text-based web browser 
IEradicator [102k] Internet Explorer (versions 3 through 6) removal tool.
KillAd v0.11 [42k] + Ad blocker. Works with IE, Netscape, and Opera. 
SAB 0.96 [93k] + Filter out web annoyances. Linux version also available.
Proxomitron [371k] + Powerful filter for eliminating web annoyances and customizing your browsing experience. 
PopKi Popup Closer v1.4 [187k] + Prevent popups without using a proxy. 
Offline Browsing & Download Managers
HTTP Get [15k] + Download files from the web 
HTTrack Website Copier 3.10 [176k] {S}+ Save entire websites to a local directory.
GNU Wget 1.8.2 [271k] {S}+ Mirroring tool which supports HTTP, HTTPS and FTP. 
Flash Movie Player 1.4 [333k] + ShockWave Flash (SWF) player with animation rewinding, advanced full screen mode, playlists, browser cache integration, snapshot creation, more. (The Green Award is given to the installer-free version (which the author kindly provided) directly linked to from here.) 
ASFRecorder V1.1 [368k] {S}+ Download and store streaming Windows Media files (asf, asx, wma, wmx, wmv, wvx). 
DLExpert [769k] Download manager with multi-thread, pause/resume, scheduling, auto dial, hangup, shutdown, more.
Email Clients
Qm [16k] + Quick mail sending program 
bmail [17k] + Lean command line SMTP mail sender 
SendMail [18k] + Send email (and even attach a file) using any SMTP serverGetmail [50k] + Console utility for downloading POP3 mail. Free for non-commercial use.
Blat 1.9.4 [74k] {S}+ Console utility that sends the contents of a file in an e-mail message using the SMTP protocol.
nPOP [82k] {S}+ Tiny email client with powerful features. Pocket PC, Windows CE, and Japanese versions also available. 
JBMail 3.2 [159k] + Portable mail client with POP3 and SMTP support, and optional SSL/TLS security. Shareware version saves multiple profiles to disk. 
SpeedMail [188k] + SMTP mailer with simple address book and attachment support. 
Popcorn 1.79 [250k] {S}+ Ultra-lightweight POP3/SMTP email client. Check/delete mail on server before downloading. 
Pimmy 3.5 [361k] + Complete email client; includes newsgroup support. 
i.Scribe [512k] + A small, fast, crossplatform, object based email client with many of the features that larger mail clients have. 
Mailing Lists
ListMaster Pro 1.00 [251k] Mailing list management
SmartSerialMail 1.1 [229k] + Group mail sender
Vallen e-Mailer R2003.0217 [324k] + Group mail sender
Other Email & Usenet
Obfusticated Email Link Creator [4k] + Create munged email address links with hex, dec, or a mix of both. 
K9 Version 1.01 [52k] + Automatic spam email filtering for POP3 email.
StripMail [256k] + Clean up emails & plain text files.
Bounce Spam Mail v.1.8 [271k] + Send fake bounce messages. Does not support SMTP authentication.
Pimmy 3.5 [361k] + Complete email client; includes newsgroup support. miniRelay 0.9.75 [269k] + SMTP relay tool that shuts down when idle. 
Xnews 4.06.22 [680k] + Usenet newsreader
HTTP, FTP, File Sharing & SSH Clients/Servers
Simple Socket File Transfer 1.0 [9k] + Transfer a file between two computers using the TCP port of your choosing. 
Atomic Web Server v1.0 [15k] {S}+ Extremely simple and fast web server 
SlimFTPd [22k] + Standards-compliant FTP server with an advanced virtual file system.TinyWeb 1.9 [53k] {S}+ Small, simple and fast Win32 daemon for regular (TCP/http) and secure (SSL/TLS/https) web servers.
BarracudaDrive V1.5.2 [196k] + Multi-user secure HTTPS file manager which eliminates the need for FTP access. Securely upload, download, and manage your files on your home computer from anywhere in the world. BarracudaDrive also bypasses firewalls and proxies since the communication protocol is HTTPS. The communication is protected by using SSL so no one can eavesdrop on your file transfer. Linux and OS X versions also available. 
RemotePad [244k] + Combination plain-text-editor and ftp-client. 
FTPpie [248k] + Pie chart display of FTP file space use.
i.Ftp 1.85 [359k] {S}+ Simple graphical ftp application. 
SendTo FTP 2.8 [359k] FTP from the context (right click) menu.
HFS - HTTP File Server 1.6a [409k] {S}+ Simple HTTP server with drag & drop interface. 
TYPSoft FTP Server 1.08 [456k] {S}+ Simple, clean and robust ftp server. 
WinSCP 3.7.4 [980k] + SCP (Secure CoPy) client using SSH (Secure SHell). Safely copy files between local and remote computers.
LeechFTP 1.3 Build 207 [580k] Multithreading FTP client
Ftp.exe [44k] + Command line FTP program included with Windows. Brief tutorial | Scripting
Telnet
SimpTerm [from 110k] + Several versions available (modem or TCP/IP; 16/32 bit). Provides VT100/ANSI Color terminal emulation and Kermit, xmodem, ymodem and zmodem file transfer capability. Supports BIG5 (tranditional), GB (simplified) and HZ encoded Chinese text.PuTTY 0.57 [372k] {S}+ A Telnet and SSH client, along with an xterm terminal emulator
Tera Term (Pro) [922k] {S} Supports serial port connections; TCP/IP (telnet) connections; VT100, select VT200/300, and TEK4010 emulation; file transfer protocols (Kermit, XMODEM, ZMODEM, B-PLUS and Quick-VAN); scripting; Japanese & Russian character sets; more. SSH module also available.
IRC
TinyIRC Beta Build 1069 [54k] + The goal of this project is to create the world's smallest IRC client for Win32, with as many (if possible, all) of the features that you're used to in your current IRC client. 0irc v1.4.53 [67k] {S}+ Tiny, open source IRC client. 
Dana 1.3 [121k] + Simple, skinnable IRC client 
IamC 2.9.26R [198k] + Simple IRC client
xchat 1.8.5 [633k] {S} Graphical IRC client for Windows and several other OSs
HydraIRC [740k] {S}+ Open source IRC client with support for: DCC chat and file transfers, connecting to multiple servers, dockable floating tabbed windows, channel monitoring, message logs, event viewer, reg-exp highlighting, and much more.
Instant Messaging (IM)
miniaim v0.2.3 [47k] + Tiny AOL instant messaging client. 
PixaMSN v0.61 [168k] {S}+ Tiny MSN Messenger clone. 
Miranda IM 0.3.3 [774k] {S}+ Streamlined ICQ client which supports ICQ, AIM, MSN, Jabber, Yahoo, Gadu-Gadu, Tlen, Netsend, and more.
Voice over IP (VoIP)
PicoPhone [88k] {S}+ Simple Internet phone application with chat 
VoIPerized [279k] Tiny Voice over IP program. Download
Speak Freely 7.6a [690k] {S} Conduct real-time voice conversations over the Internet or any other TCP/IP network. Includes IDEA, DES, and limited PGP encryption capabilities.
Port-to-Process Mappers
DiamondCS OpenPorts v1.0 [24k] + CLI port to process mapper for Windows NT/2000/XP. Provides five different output styles, including CSV, FPort, and WinXP's Netstat. Free for personal use. 
CurrPorts v1.02 [36k] + Detailed view of open ports and their corresponding applications. Close ports, kill processes, export info to HTML, XML, or CSV, and much more.
Remote Access
ZeroRemote v1.2.5 [152k] + Remote viewer with DirectX support, file transfer, audio, and more. Single EXE supports both client and server modes. 
TightVNC 1.2.8 [582k] {S}+ Client/server software package allowing remote network access to graphical desktops. This bandwidth-efficient version has many improvements over the original.
Network Speed Testing
NetCPS [23k] {S}+ Measure the effective performance of a TCP/IP network. 
PCATTCP [60k] {S}+ PCAUSA's port of Test TCP (TTCP), a command-line sockets-based benchmarking tool for measuring TCP and UDP performance between two systems. 
Ping / Network Scanning
Angry IP Scanner 2.21 [109k] {S}+ Pings a range of IP addresses and optionally resolves hostnames, scans ports, returns NetBIOS info (computer name, workgroup name, currently logged in user and MAC address), and saves results to CSV, TXT, HTML, XML or IP-Port list files. (While settings can be saved to the registry, this is not the default behavior.) 
MultiPing Grapher 1.4.1 [284k] + Graph up to 10 different ICMP results. Adjust ping interval and packet size. Includes logging and average calculation.
PingPlotter 1.10 [424k] Graphical network troubleshooting and diagnostic tool. Shareware version also available (feature comparison).
SoftPerfect Network Scanner 3.3 [619k] + IP, NetBIOS, and SNMP scanner with a slew of features: fast multithreaded scanning; computer pinging; hidden shared resource detection; scanning for listening TCP ports; mount and explore found resources; resolve host names; autodetect local and external IP range; support for remote shutdown and Wake-On-LAN (WoL).
Other Network Tools
IP List [12k] + Enumerates network interfaces, showing all bound IP addresses, their broadcast addresses, and their netmasks. Resolve [16k] + Resolve an IP address to its DNS address, and vice versa. XWhois [21k] + Look up information on registered Internet domains and addresses.ShareWatch 1.0 [33k] + Monitor shares on local and remote servers; see who is connected and what files they are accessing; disconnect any file, user, computer, or share; more.
Netcat 1.11 [60k] {S}+ Network swiss army knife. Review 
TCP Optimizer [425k] + Optimize your Internet connection
SoftPerfect Personal Firewall 1.2 [900k] "Does not change your Windows system files and does not require any additional libraries"
HTML and Webmaster Tools
TAGCASE [6k] {S}+ Converts the case of HTML tags without disturbing attribute values. KILL 1.5a [from 8k] + Removes all HTML tags and JavaScript from one or more HTML files. DOS and Windows versions included. HTMStrip 911 [129k] + Convert HTML to plain text. Very robust command line program.HTML stripper 1.1 [275k] + Scrub HTML clean of ads, iframes, scripts, etc.
Text2HTML 1.3 [240k] Convert plain text to HTML 
HTML Image Page Builder [193k] + Convert images to HTMLSplitz [353k] + Split any image into rectangular parts and export the resulting images along with the HTML table that puts them back together.
sHTMLc v2.0 [148k] + Convert characters to character entities quickly and easily. 
TidyGUI 1.1.5 [146k] {S}+ Clean up your HTML
Xenu's Link Sleuth 1.2d [230k] + Check websites for broken links
Domain Name Status Reporter [328k] + Monitor the registry status of domain names.
Webalizer [794k] {S}+ Web server log file analysis program. Produces highly detailed, easily configurable usage reports in HTML format.
Graphics
Viewing & Editing
EVE 2.27 [55k] + Vector graphics editor 
PictView 1.94 [104k] + Multi-format image viewer and converter. DOS and Windows versions available. 
i.Mage v1.05 [663k] {S} Graphics editor "designed to be a better Deluxe Paint IIe"
IrfanView 3.80 [822k] + Graphic viewer & editor. Tutorial
XnView 1.66 [898k] + Graphic viewer and converter with support for more than 400 formats. Many *nix ports also available.
Measuring
Screen Calipers v1.0 [136k] + Measure screen objects in pixels using a calipers 
JR Screen Ruler [100k] + Measure anything on your screen in pixels, inches, picas or centimeters
Optimizing
JPG Cleaner 2.6 [from 8k] + Strip non-picture data from JPGs. Several versions included.
jhead 2.3 [94k] {S}+ Extract/modify digital camera setting information from exif JPEG files, strip unncessary data, more. Precompiled binaries available for Windows, OS X, Linux, FreeBSD, and Solaris. 
pngquant [109k] {S}+ Command-line utility to quantize and dither 32-bit RGBA PNGs down to 8-bit (or smaller) RGBA-palette PNGs, usually with a significant reduction in file size. Batch processing, palette optimization, more. Pngcrush [146k] {S}+ PNG optimizer with binaries for several platforms GIF Optimizer v1.0 [258k] + Reduce the size of GIFs. Trout's GIF Optimizer [365k] + Shrink GIF files. Batch processing, color palette reduction, more. Donation required to remove nag. 
Screen Capture
Screen Thief for DOS v2.01 [37k] + Capture DOS screens as BMP, TIFF, PCX or TXT files.
MWSnap [601k] + Screen capture program which supports BMP, JPG, TIFF and GIF formats. Custom color depth & quality settings, zoom, screen ruler, and color picker.
CamStudio 2.0 [1331k] {S} Screen recorder able to save captures as AVI or SWF (Flash) files. (Source code available here)
Fonts
FontSelector 1.3 [277k] + Browse and print all your installed fonts.
The Font Thing 0.80 [483k] + Powerful TrueType font manager
Other
jRes [5k] {S}+ Switch screen resolution or color depth from the system tray. WHATPIC 4.0 [18k] + Command line utility that returns the format, width, height, number of colors, filesize and drive volume of graphic files.Fatbits [32k] + Screen magnifier
IconShop 1.13 [90k] + Manage icon libraries
Nadger 0.5 [213k] + Color grabber which returns hex, websafe, and RGB values. Save colors to custom groups. 
Resize 2.6 [335k] + Batch resize images by percentage, height, width, or maximum dimension while maintaining aspect ratio. From the website: "The resizing algorithm produces high quality images because it uses all available information from the source image. Most other image resizing software only use a small amount of information from the source image." 
Easy Thumbnails [542k] + Thumbnail generator from the maker of NoteTab. Compressed version
Metamorph 3D [578k] + "Fast, sleek, little image morphing utility" 
YASRT v0.1 beta 12 [890k] + Yet Another Simple RayTracer. Generates realistic pictures from text descriptions. Versions available for a wide range of OSs.System
BIOS/CMOS
WipeCMOS [1k] + Clears all CMOS settings to recover from lost passwords or corrupt BIOS settings. BIOS [24k] + Saves and restores BIOS settingsOSs, Boot Disks, etc
QNX Demo Disk [1400k] + "A Web browser, a web server, a POSIX-certified realtime OS, TCP/IP and a windowing system on a single 1.44 Mbyte floppy disk." (Note: QNX has removed the Demo Disk from their website and has not responded to my phone calls and emails to restore it or allow me to post it here. The link, therefore, points to the Wayback Machine's cached version. You can find the downloads here.) 
MENUET OS [1420k] {S}+ "An OS written fully in 32 bit assembly. It's a Real-Time, graphical OS for 32 bit asm programming, and it fits on a single floppy." 
KolibriOS 0.7.7.0 [1440k] {S}+ A small x86 assembler hobby operating system, forked from MenuetOS in 2004. 
Visopsys 0.69 [1440k] {S}+ A fully multitasking, 100% protected mode, virtual-memory, massively-monolithic-style kernel with a bare-bones C library and minimal suite of applications. 
colorForth [63k] {S}+ An OS, development system, and language rolled into one. 
FREESCO [1330k] {S}+ Router with many features of a full OS. Easy to setup and can be run off a single floppy.The Ultimate Boot Disk 4.3m [615k] + Partial list of features: Restores system files, installs Windows faster, identifies PC hardware, extracts Windows cd files, troubleshoots startup errors, clones drives or partitions, streamlines the registry, optional virus scanner.
Bart's Network Boot Disk [390k] + Network boot disk with PCI NIC auto-detect, support for TCP/IP, Nwlink and Netbeui, over 100 driver plugins available. 
The BootDisk Project & Bootdisk.info provide a wide variety of bootdisk images.
Unix, GNU, etc
Explore2fs 1.07 [384k] {S}+ GUI explorer tool for accessing ext2 and ext3 filesystems.
Berkely Utilities [819k] + A set of 40 UNIX-like utilities for MS-DOS, each around 20k. Formerly $200, now free. Includes: awk, basename, cal, cat, cb, cmp, comm, cp, cut, df, diff, dtree, du, ech, ed, expand, find, grep, head, join, ls, make, more, mv, od, opts, paste, rederr, rm, sed, sort, split, tail, tee, touch, tr, unexpand, uniq, wc, which, xstr. Swiss File Knife File Tree Processor [1096k] + A veritable treasure chest of functionality bundled up into a single EXE: grep, tree size list, instant FTP/HTTP server, text line filter, text replace, duplicate file finder, split/join files, create MD5 lists, run command on many files, extract strings, and much more. 
Unix Tools [1166k] + 17 Unix utilities that execute from one EXE without ever extracting to disk. Includes: Bash, Less, Gzip, Grep, Find, Df, Du, Ls, Cat, Cp, Mv, Ps, Rmdir, Mkdir, Rm, Pwd, Tar.Cygwin-Lite [1280k] {S} UNIX-like command-line environment for Win9x/Me/NT4/2000
GNU utilities for Win32 [1454k] {S}+ Over 100 GNU apps ported to native Win32 (see this post for more information). 
GNUWin32 [various sizes] {S}+ Over 150 GNU apps ported to native Win32.
Google's listing of floppy-sized Linux distros
Macintosh
Gemulator Explorer [30k] + "Access and copy files from any Macintosh 1.44M floppy disk, Macintosh CD-ROM, Macintosh ZIP disk, external Macintosh SCSI hard drive, Atari ST formatted floppy disk, Atari ST ZIP disk, Atari ST formatted hard drive, and even disk image files." 
HFVExplorer [405k] + Access Mac disks under Windows
Registry, Cleaning, & Tweaking
Regcmd 0.88a [25k] Command line based Registry editor. 
RegShot v1.7.2 [28k] {S}+ Uncover registry changes 
Tweak UI 1.33 [64k] Tweaks for the Windows User Interface
Regmon [72k] {S}+ Monitors and displays all Registry activity
Test-Run 2.1.0 [136k] Protects the registry while testing new software.
RegSeeker [242k] + Powerful registry cleaner and more. Free for personal use. 
98lite [349k] $ Remove web integration and many other resource-hogging "features" from Windows 98/Me.
RegCleaner [540k] "Easily get rid of those old and obsolete registry entries created by software that you have destroyed ages ago."
Startup Managers
StartupRun v1.20 [27k] + A better msconfig.
A-spy 0.0.9 [318k] + Startup manager with an "About" box which provides scads of live system info. 
Process Monitoring & Terminating
AppSwat v1.3.0.0 [8k] + Process terminator. Command-line termination, system startup integration and an effective termination mechanism. 
Procmon [33k] {S}+ View, terminate, and prioritize active processes
PrcView 3.7.2.5 [92k] + Process viewer/killer. Includes both GUI & CLI versions.
Process Explorer [230k] + Process viewer/killer. Displays process icon, command-line, full image path, memory statistics, user account, security attributes, DLLs. Also includes search function.
System Info & Diagnostics
Uptime [6k] + Displays uptime in console UpTime 1.0 [13k] + Displays up-time in a tooltip from the system tray 
MemTest 3.8 [15k] + RAM reliability tester that runs under Windows. 
CPU Info [17k] + Determines CPU type, vendor, serial number, and clocks CPU speed. Infoman2 [20k] + Tiny display of available free physical memory and system resource data. 
MyCPU 1.13f [47k] + Displays CPU info: vendor, type, model, stepping, speed, cache, more. 
Memtest86 3.0 [51k] {S}+ A thorough, stand alone memory test for x86 architecture computers.MBProbe 1.30 [68k] + Monitors voltages, temperatures and fan speeds using hardware monitoring chip(s) available on many modern motherboards
TinyResMeter [92k] + System resource information tool 
SpinRite 5 [95k] $+ "The most capable, thorough, and reliable utility that has ever been created for the long term maintenance, recovery, and repair of mass storage systems." 
WinAudit v1.2.2 [112k] + System info tool that lists: installed software, license information, peripherals, memory usage, processor model, network settings and more. Reports can be saved in several file formats. 
HD Tune [131k] + Hard disk utility which reports drive info, health, and benchmarks. PCI [164k] {S}+ Produces detailed report of all connected PCI, AGP & CardBus devices, including the system chipset. CPU-Z 1.30 [296k] + Displays CPU, Motherboard, Memory, and System info. 
Unknown Devices [392k] {S}+ Determine the identity of unknown devices in Device Manager. 
NSSI [397k] + Hardware information tool with many advanced featuresBelarc Advisor [565k] "Generates an HTML profile of everything installed on your computer, from your main circuit board to software. Version, manufacturer, and serial numbers are listed, as well as statistics such as available memory slots and hard drive space." Free for personal use.
PCISniffer 1.2 [675k] + Bootable floppy that detects and displays all PCI busses and devices. Database includes approx. 4000 devices and 1500 vendors. 
AIDA16 [1054k] + System information program. Extracts details of all components of the PC. Can display information on the screen or write it to file. 
Other
DDL [4k] + Load DOS device drivers from the command line, without having to reboot. XMSDSK & EMSDSK [75k] + A RAM disk which can be created, resized, and destroyed from the command line Filemon [76k] {S}+ Monitors and displays file system activity in real-time
Virtual Disk Driver (VDK) 3.2 [100k] {S}+ Mount VMWare virtual disks and raw sector images (made with tools like ddrescue) under 32-bit versions of Windows NT/2000/XP/2003.
Boot Log Analyzer [234k] + BOOTLOG.TXT filter 
OllyDbg v1.10 [1085k] + 32-bit assembler-level analyzing debugger for Microsoft Windows with intuitive interface. Emphasis on binary code analysis makes it particularly useful in cases where source is unavailable. It predicts contents of registers, recognizes procedures, API calls, switches, tables, constants and strings, locates routines from object files and libraries, allows custom labels and comments in disassembled code, writes patches back to executable file and more. 
