Virus/Spyware            

NoHijack - removes hijacker toolbars.

AVG anti-virus - (from Author's Site) free to home users.

AVG anti-virus - from alternative Site (majorgeeks)

Spybot- Search & Destroy - an excellent free application for killing and preventing spyware.  It has a feature for browsers that will alert you when a site is trying to infect you.

Adaware  - also removes spyware; also free.

Spywareblaster  - free, effective spyware prevention.

HijackThis! - a great utility for identifying and removing spyware; takes some thought.

Stinger - limited but effective stand alone virus scan from macafee.

CWShredder - a small, effective utility for removing Cool Web Search variants.

Zone Alarm - excellent firewall free to individuals and non-profit organizations; takes some initial learning. There are options to buy; the free one is called simply Zone Alarm.

Ca Global Security Advisor -  comprehensive information on Spyware.

Updates Page - live feeds from Trend Micro and Sophos ; links to anti-virus updates and removal tools.

Security

Gibson Research Corporation- security tests and excellent information about  Windows vulnerabilities and some solutions.

Browser Security Test   - tests 20 vulnerabilities, with links to existing patches.

Mozilla Firefox - if you've run the browser test above and were surprised by the number of vulnerabilities in Internet Explorer, you're not alone. Even the United States Computer Emergency Readiness Team (US-CERT), a division of the Department of Homeland Security, is recommending switching to an alternative browser.  Mozilla Firefox is free, easy to use, and looks good.  It will import your favorites and settings from IE, and their site has good instructions on switching.