Screen capturing

Command-Shift-3 » Make a screendump of the whole screen, save to disk
Command-Shift-4 » Make a screendump of (crosshair) selection, save to disk
Command-Shift-3 while selecting press Control » Make a screendump, place in Clipboard
Command-Shift-4 while selecting press Control » Make a screendump of (crosshair) selection, place in Clipboard
Command-Shift-4 together with Spacebar » Select window, then Make a screendump of the selected window
Command-Shift-4 together with Spacebar while selecting press Control » Select window, then Make a screendump of the selected window, place in Clibboard

N.B. Extra screen capture features available in Mac OS X Leopard
Begin taking a screenshot by pressing
Shift-Command-4, then start dragging. Then press and hold the following keys while still dragging to modify the selection before letting go and taking the shot:

  • Space Bar » moves the selection while maintaining the current size
  • Shift » locks the x or y axis, depending on which direction you move the mouse after holding the Shift key down (for example, hold Shift and move up or down to keep your selection the same width, or press and hold Shift and e up or down to keep your selection the same width, or press and hold Shift and move left or right to keep your selection the same height.)
  • Option » changes your selection mode to resize from the center out as opposed to from one corner to another.
Source: Mac OS X Hints - 10.5: Use extra region capture screenshot options

Pressing the escape key before releasing the mouse button will cancel the screen grab.

Remarks
  • 'Command' also known as 'Apple key' (⌘; the Apple key symbol apple disappeared from keyboards released on august 7th 2007 and later)
  • 'Option' also known as 'Alt'
  • Function also known as Fn

» Overview of the keyboard symbols