This is one of the first questions I had when I got this new laptop. It’s fairly simple (even if it isn’t all too memorable).
Command-Shift-3: Capture the entire screen and save it to a file on the desktop
Command-Shift-4 and then select an area: Capture a defined area of the screen and save it to a file on the desktop
Command-Control-Shift-3: Capture the entire screen and save it to the clipboard
Command-Control-Shift-4 and then select an area: Capture a defined area of the screen and save it to the clipboard
Alternately, you can use the grab utility within OS X.
