If you are a Switcher or you just happen to be new to Mac, you should definitely check out Apple's Mac 101 Guide to using your Mac effectively and efficiently. The site includes a basic walk through of your Mac with other introductory materials.
One of the coolest bits, mentioned over at fscklog, is the My Mac Cheatsheet, a downloadable PDF containing all the vital information that you need to remember about your Mac: "Whether your Mac asks you for certain information or you're seeking help from Apple or an Apple Authorized Service Provider (AASP), there may come a time when you need to have your various passwords, dial-up numbers, mail server addresses, email addresses, hardware specifications, serial number, and other information handy. And then you discover that you've either forgotten or misplaced this information."
These sheets could also be useful for anyone managing multiple Mac users in an office environment. Require all users to fill out these forms and either require them to present the forms for service or keep all the vital info locked up in a file box for whenever you have to fix someone's machine.