I have used many of these programs on a regular basis, although, some of them I have just found but I do intend to use.
I suppose the bias on this list is towards creative and communications software, because that reflects my own bias.
Many of the programs are open source but by not all of them, quite a few are free for personal use versions of commercial software.
Web BrowserFirefox - Tabbed browsing from the ashes of Mozilla.
Opera - Now free.
RSS ReaderRSS Owl - RSS feed aggregator.
FTPFilezilla - FTP Client and server.
HTML editorNvu - Another program from the ashes of Mozilla.
"LAMP" for WindowsXampp - Linux, Apache. MySQL, PHP - web development environment.
Office toolsOpen office - Office suite.
Dia - Diagram maker.
Open workbench - Project type program.
Free mind - Mind mapping software.
Foxit Reader - Small, fast and free.
PDF creator (makes PDF's. Open office also allows export as PDFs).
GraphicsWin Gimp - Image editing.
Picasa - Image viewer.
Inkscape - Vector drawing.
Qcad - Computer Aided Design.
Scribus - Desktop Publishing (currently first Beta for Windows).
3d graphicsBlender - Cross platform 3d modeling.
Avimator - Avatar animation editor.
Moving imageJahshaka - Promising, but not yet very polished.
Democracy - Video catcher and player (developing into an internet TV platform).
Video Lan - DVD player
AudioAudacity - sound editor
Lame - mp3 codec (needed by Audacity to save projects as mp3s).
Juice - Pod catcher
CDex - Rip your CDs to MP3
Winamp - Many people are very fond of this player.
Misc Utilities7zip - Like winzip, but free.
RealVNC - By the people who brought you VNC.
Spybot: Search and Destroy - Searches and destroys spyware.
AdAware Personal - Another Spyware search and destroyer.
AVG Free - Free Virus checker.
ClamWin - Free Open Source virus checker.
Kerio Personal Firewall - My free firewall of choice.
Net Stumbler - Find out what's in the ether.
Belarc Advisor - Find out what's on your PC.