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