Core security resources, those usually labelled "security". Check Wayne's Windows NT, Windows 2000, Windows XP, Firewall and VPN, or Penetration Testing (anti-hacker) sites for resources focused on those areas. If there is a dead link or a valuable resource missing, please let me know: Wayne Maples.

• Microsoft Security Resources
  If your focus is a Windows-based platform, this link is key. Go there. Bookmark it. But don't neglect non-Microsoft resources like those listed below.

• Security Associations / Security Portals / Hacking Portals :
  • BlackCode
    
  • Center for Internet Security
    
  • CERT Coordination Center
    
  • GCK's Security-related URLs
    
  • IEEE Computer Society
    
  • IllegalWorld
    
  • Information Systems Security Association (ISSA)
    
  • InfoSysSec
    
  • Insecure : exploit world
    
  • (ISC)2 International Information Systems Security Certification Consortium
    
  • Mitre : common vulnerabilities and exposures
    
  • Open Web Application Security Project (OWASP)
    project is developing software tools and knowledge based documentation that helps people secure web applications and web services.
    
  • Packet Storm
    
  • SANs
    
  • SearchSecurity : security info site
    
  • SecurityFocus
    
  • TruSecure
    
  • W3C Security Resources
    
• Security Book Recommendations:
  • General Security Texts
    
  • Hacking, Intrusion Detection, and Penetration Testing
    
  • Windows NT Security Texts
    
  • Windows 2000 Security Texts
    
  • Windows XP Security Text
    
• Security Checklists / Guidelines / Reports:
  • Administrator's Workstation, Protecting Hardening
    
  • Basic Security Checklist for Home and Office Users
    
  • Improving Computer Security through Network Design
    
  • Local Area Network Security Guidelines
    
  • Microsoft Security Checklists
    
  • Microsoft's The Ten Immutable Laws of Security
    
  • NIST's Information Technology Laboratory Security Bulletins
    
  • NT :
    • Armoring NT
      
    • Burton Group's NT Security
      
    • C2 NT Configuration Checklist
      
    • Checklist, Out-of-the-Box NT Security Checklist
      
    • Hardening NT pdf
      
    • Lock the Doors on Windows NT in 10 Steps ZDNet article
      
    • Security Guidelines, Trusted Systems' Windows NT Security Guidelines
      
    • Security Steps for NT
      
    • System Security Administration for NT using Perl
      
  • Open Source Security Testing Methodology
    
  • RFC1244: Site Security Handbook
    
  • SAN Information Security Reading Room 500+ documents
    
  • Windows Security Guides : IE, Win9x, NT/W2K/XP
    
  • Windows 2000, Hardening pdf
    
  • Wireless LAN Security
    
• Security Policies / Practices:
  • CERT Security Improvement Modules
    
  • Sample security policies and guidelines
    
  • Security Manager's Journal
    
  • Information Security Policies, Procedures, and Standards: Guidelines for Effective Information Security Management
    
• Security Vendors:
  • e-Security integrators
    
  • eSoft's InstaGate Product Line
    
  • iDefense
    
  • IntelliTactics : Network Security Manager
    
• Penetration Testing Vendors:
  • Corsaire UK, Europe
    
  • Foundstone Hacking Exposed book guys, Ultimate Hacks classes, Professional PT services