Like minded friends
Gryphn
Mike Neir
Shelby
Phildo
Billy (Billweiser.com)
Server Monk
Security Related
SecurityFocus.com – Excellent all around news site
NSA – Security configuration guides for many OS and hardware types
cert.org – Unix secure configuration guidlines
rainbowtables.net – Huge, searchable database of known hashes and their plaintext equivalent. Scary concept, useful tool.
Anonymos Proxy Sites – Large list. Useful for testing external connectivity or bypassing filtering proxys.
insecure.org – makers of nmap network/port scanner and keepers of the list of the “Top 100 Network Security Tools“.
schneier.com – Schneier on Security, personal blog of security guru Bruce Schneier. Author of Blowfish, many good books and owner of Counterpane Internet Security.
Packet Storm – Large archive of news, tools and (most notably) exploit code.
SANS – Keepers of the ineternet storm center, the GIAC certifications and the sans portal.
Forensics and Incident Response
US Secret Services – Best Practices for Seizing Electronic Evidence
SysInternals.com – Makers of some of the greatest forensic tools ever. All free