Bolded items are software that casual users would likely install and use.

Productivity

• http://www.openoffice.org/ - OpenOffice free productivity suite, (replaces MS Office)
• http://www.mozilla.com/en-US/ - Firefox Web Browser (replaces Internet Explorer)
  
• http://www.mozilla.com/en-US/thunderbird/ - Thunderbird Email Client (replaces Outlook Express)
• http://www.7-zip.org/ - File Archiving/Compression - (7z, ZIP, GZIP, BZIP2 and TAR files)
• http://peazip.sourceforge.net/index.html - file and archive manager - (7Z, ARC, BZ2, GZ, PAQ/LPAQ, PEA, QUAD/BALZ, TAR, UPX, ZIP)
• http://www.pidgin.im/ - Universal IM client (AIM, IRC, Yahoo!, Google Talk, Sametime, MSN, XMPP, etc.)
• http://www.primopdf.com/ - Create PDF files from any program that can print, installs as a "printer".
• http://www.educ.umu.se/~cobian/index.htm - Cobian Backup multi-threaded program that can be used to schedule and backup your files and directories from their original location to other directories/drives in the same computer or other computer in your network. FTP backup is also supported in both directions (download and upload)
• http://www.scribus.net/ - professional page layout with "press-ready" output

Security

• http://free.avg.com/download-avg-anti-virus-free-edition - Free Anti-virus (replaces Mcafee, Norton)
• http://www.clamwin.com/ - Free Anti-virus (replaces Mcafee, Norton)
• http://www.lavasoft.com/?domain=adaxis.net - Ad-Aware Anti-Spyware
• http://www.spybot.info/en/download/index.html - SpyBot Anti-Spyware
• http://www.truecrypt.org/downloads.php - TruCrypt - File/Disk Encryption Software - Consider using this for any personal files on USB drives.
• http://www.cezeo.com/products/disk-redactor/ - Clear disks data from deleted files. Assures that files CANNOT be recovered.
• http://eraser.heidi.ie/ - Clear disks data from deleted files. Assures that files CANNOT be recovered.
• http://www.wireshark.org/ - network traffic analysis
  
• http://ettercap.sourceforge.net/index.php - sniffing of live connections, content filtering on the fly

Backup

• http://areca.sourceforge.net/ - Areca is a personal file backup software developed in Java.

Image/audio/video creation, editing, & processing

• http://www.photoscape.org/ps/main/index.php - Photo cropping, repair, Animated GIF creation
• http://www.faststone.org/ - FastStone Image Viewer
• http://www.gimp.org/ - GIMP - GNU Image Manipulation Program (replaces Photoshop)
• http://www.inkscape.org/ - Vector Graphics Editor (SVG - Illustrator, CorelDraw, or Xara X)
• Audacity - Audacity® is free, open source software for recording and editing sounds. It is available for Mac OS X, Microsoft Windows, GNU/Linux, and other operating systems.
• http://www.videolan.org/vlc/ - VLC media player (windows media player)
• http://sourceforge.net/projects/ffdshow - DirectShow and VFW codec for decoding/encoding many video and audio formats
• http://sourceforge.net/projects/guliverkli/ - MediaPlayer classic - Plays many media files
• http://download.videohelp.com/tin2tin/features.html - DVD slideshow GUI - images to video with transitions, pans, zooms, effects
  
• http://mediacoder.sourceforge.net - universal batch media transcoder
• http://juicereceiver.sourceforge.net/index.php - Juice podcast receiver
• http://handbrake.fr/?article=details -  multithreaded video transcoder, convert DVDs to Video Files
  
• http://audacity.sourceforge.net/about/ - Audacity audio editor and recorder
• http://www.dvdflick.net/ - DVD Flick - DVD Authoring tool
• http://www.dvdstyler.de/ - DVD Styler - DVD Authoring tool
• http://ekiga.org/index.php?rub=1 - Ekiga - VoIP and video conferencing application
• http://www.ephpod.com/ - iPod download tool
• http://www.mixxx.org/ - DJ Live Mix software
• http://www.debugmode.com/winmorph/ - high performance morphing and warping software.
• http://www.debugmode.com/wax/ - high performance and flexible video compositing and special effects software
• http://www.debugmode.com/wink/ - Tutorial and Presentation creation software, you can capture screenshots, add explanations boxes, buttons, titles etc
• http://www.nchsoftware.com/slideshow/ - Create video slideshows from images. Supports soundtracks, pan/crop/zoom, transitions, etc...
  

Connectivity

• http://www.chiark.greenend.org.uk/~sgtatham/putty/download.html - PuTTY SSH/SCP clients
• http://www.aboutmyip.com/AboutMyXApp/DeltaCopy.jsp - Rsync Client & Server
• http://openvpn.net/ - VPN Client & Server
• http://www.uvnc.com/ - UltraVNC - Remote Control of a system, Client & Server
• http://mobassh.mobatek.net/en/ - SSH server for windows based systems
• http://mobaxvt.mobatek.net/en/ - MobaXVT - Portable X server with cygwin utilities
• http://www.straightrunning.com/XmingNotes/ - XMing XServer
• http://www.cezeo.com/products/nir/ - Show network information to assist in debugging network issues
• http://azureus.sourceforge.net/download.php - Vuze Bittorrent Client
  
• http://www.fs-driver.org/ - full access to Linux Ext2

Utilities

• http://sourceforge.net/projects/lightscreen - Screen capture utility
• http://infrarecorder.org/ - CD/DVD burning solution
• http://gnuwin32.sourceforge.net/ - Standalone (does not require cygwin) UNIX utilities for Win32.
  

Web / Development

• http://kompozer.net/ - HTML/CSS  -Web Authoring System (Dreamweaver, Contribute)
• http://www.httrack.com/ - HTTrack is a free and easy-to-use offline browser utility.
• http://filezilla-project.org/ - FTP/FTPS/SFTP client & server
• http://winscp.net/eng/docs/introduction - SFTP client and FTP client
• http://bluefish.openoffice.nl/ - Bluefish is a powerful editor targeted towards programmers and webdesigners.
• http://seleniumhq.org/ -  Web App Testing and Automation
• http://www.bonitasoft.com/ - Workflow development and processing.
• http://www.processmaker.com - Workflow development and processing.

MISC

• http://portableapps.com/ - Many PORTABLE applications that can be installed on a USB Drive, don't have to be install on a system. Very helpful when using systems that are not your own, like library systems, college lab systems, etc.