Anti-Spyware:
Super Anti-Spyware - Scan and clean (recommended)
Spybot - Search & Destroy - Popular free Spyware scanner/cleaner
Ad-Aware Personal - provides advanced protection from known data-mining, aggressive advertising, trojans, dialers, malware, browser hijackers, and tracking components. This software is downloadable free of charge.
PC Tools ThreatFire - Add-on to existing anti-virus to add "zero-day" protection against viruses and spyware not yet detectable by anti-virus software--free for home users.

Anti-Virus:
AVG Anti-Virus - Free Anti-Virus software for home users (recommended)

Free Tools:
CutePDF - Create Adobe Acrobat files, for free!
Free Download Manager - Accelerates Windows downloads

Other Free Software:
deBlor blog - Free software for Windows Mobile Pocket PCs
Microsoft Download Center - Software, Updates, and Service Packs