WinPatrol will sniff out Worms, Trojan horses, Cookies, Adware, Spyware and other malicious programs that may attack your computer.

Spybot - Search & Destroy can detect and remove spyware of different kinds from your computer. Spyware is a relatively new kind of threat that common anti-virus applications do not yet cover. If you see new toolbars in your Internet Explorer that you didn't intentionally install, if your browser crashes, or if you browser start page has changed without your knowing, you most probably have spyware. But even if you don't see anything, you may be infected, because more and more spyware is emerging that is silently tracking your surfing behaviour to create a marketing profile of you that will be sold to advertisement companies.

If you are using a cable modem, security is most likely one of your 
concerns (if not, it probably should be). To see how secure your 
system really is, you can try two Internet sites: 

http://www.grc.com and http://cgi.spaceports.com:81/ 

Both of these sites check your computer, looking for entry points. If you discover that your system is not very secure, go to 

http://www.zonelabs.com/download_ZAfree.htm 

and download the latest ZoneAlarm (currently 2.1). After you install 
ZoneAlarm, go back to the security sites listed above and check your 
system again. You may be surprised at what you find--or don't find. 

Ecertify Information Security sytems

Fred's PGP Page PGP is 'Pretty Good Privacy'. It is a publically available encryption scheme that allows Internet users to send encrypted messages to each other via the Internet

Firewalls For Home Users Are Essential

Firewall Forensics (What am I seeing?)

TopClick The Internet's Private Search Engine

Security Focus.com

Free software to check your system for spyware. 
What is sypware ?

Working to Halt Online Abuse

Zone Alarm Always-On Internet Firewall Security Software