It’s amazing how much free, quality, software is available. Here’s a short list of some of the free stuff that I’ve used and like.

7-Zip – file compression and extraction
AboutTime – automatically sets your computer’s clock
Avast – virus scanner
Startup Control Panel – manages the programs that run on startup
CDex – rips music CDs
Daemon Tools – mounts .iso files
DVD Shrink – rips DVDs (for backup!)
Ethereal – network traffic analyzer
Filezilla – FTP client
Gaim – multi-protocol IM client
Google Desktop – desktop search
Mozilla Firefox – web browser
Mozilla Thunderbird – email client
SpaceMonger – disk usage visualization
TrueCrypt – file encryption
Winamp – MP3 (and more) player

Here are some applications that I’d like to find something better (still free). If you have any suggestions, let me know.
text/html/code editor
rss/podcast manager
desktop search
operating system
photo manager
image editor