Anti-Virus Software
AVAST
AVG
Trend Micro (free web based online scan)

Firewalls
ShieldsUP!
ZoneAlarm

Spyware/Adware Tools
Spybot
Ad-Aware

Operating System and Application Patches
Windows Update
MS Office Update
Apple OS X Update
IBM Thinkpad/Lenovo Updates

Document Readers
Acrobat Reader

PDF Writers
Cute PDF
PDF 995

Compression Tools
Free Zip
Quick Zip