SysAdminGear

http://www.nsa.gov have some security guides in PDF

Security Configuration Guides Operating Systems on this site:
- Apple Mac OS X 10.3 'Panther'
- Apple Mac OS X 10.4 'Tiger'
- Microsoft Windows XP
- Microsoft Windows 2000
- Microsoft Windows Server 2003
- Microsoft Windows Vista
- Red Hat Enterprise Linux 5
- Sun Solaris 8
- Sun Solaris 9

Consult it here:
NSA operation system security guides