Apple's NetInfo Documentation (2,870)
A 1.9mb PDF file discussing the details of using NetInfo in OS X. Written from an OS X Server perspective, but should be generally applicable to OS X Consumer as well.
Apple's OS X Resource Directory (1,940)
A one-page collection of things to help with the OS X transition -- training, support, community, book references, URL's, etc. Most of the content is repeated elsewhere, but this page pulls it all together nicely.
Apple's OS X Security overview (1,222)
Targeted at the web developer, but useful to everone, this overview of OS X security explains permissions and accounts, and includes links to other resources with additional info.
Apple's OS X Security Page (1,720)
A good overview of OS X security, along with a pointer to a mailing list, if you have more interest in the topic.
Apple's OS X System Overview (3,003)
An incredibly thorough 2.9mb PDF file covering all major areas of Mac OS X, including the file system, frameworks, user experience, etc. A bit too technical for the average user at times, but still a worthwhile read-through.
Apple's OS X Updates page (1,386)
A great chart showing exactly what updates need to be applied to get from one version of OS X to the most recent.
Apple's PC/Mac sharing how-to (6,481)
A very well written explanation of Mac to PC filesharing. Includes information on command-line usage, as well as compiling and installing Samba, to make your Mac visible to the PC network.