Security community:

http://www.security-forums.com
http://www.securityfocus.com

Personal firewalls:

http://www.zonelabs.com
http://www.symantec.com

Broadband/DSL firewalls and routers:

http://www.linksys.com
http://www.dlink.com

Anti-virus software

http://www.avg.cz
http://us.mcafee.com

Spyware detection:

http://www.lavasoftusa.com
http://www.spychecker.com/program/hijackthis.html