Apple maintains a regularly updated list of keyboard shortcuts for Mac OS X at the Apple Support Web site. Along with key combinations for opening and closing windows, jumping to your Home directory and adding items to the Sidebar, the Web page also deciphers the symbols that represent the Control, Option, Command and Shift keys.
As if that isn’t enough, the keyboard shortcuts Web page also includes links to support documents that list shortcuts for other Apple applications like Keynote, iPhoto, iTunes, iCal, and more.