NSA information assurance operating system guides

The NSA has published a number of security guidelines for Apple OS X, Windows 2K, XP, 2003 and Sun Solaris 8 & 9. The Guides are about as detailed as you could expect from a government agency of the size and class of the NSA (extremely detailed).

See: http://www.nsa.gov/snac/downloads_os.cfm?MenuID=scg10.3.1.1