OSX / Mac Screen Capture Tricks

Quick way to capture just a window: Cmd-shift-4
you can drag out an rectangle,
or press space bar (icon will change to camera)
window below will change blue, click on it to get the whole window.
Press 'esc' to cancel.

Screen shot of entire screen:  Cmd-shift-3
if you have multiple monitors,
a .png file for each.

These create a .png file on your desktop.

If you hold down ctrl, it is only copied to the clipboard.  Then, you can paste it to preview (New from clipboard) or other graphics program.

There is also a Grab utility (in /Applications/Utilities) included with OS X:
Cons:   creates .tiff files only (not as convenient for me)(easily converted with Preview, just Save As..  and change the format)
Pros:  timed capture allows you to get pulldowns, also mouse pointer can be included (see Preferences..)

Some of these tricks from (orginal article no longer available):
Wayback machine: usingmac.com/2008/12/21/mac-screen-capture-tricks

even more tricks here:
http://www.tekrevue.com/tip/how-to-customize-screenshot-options-in-mac-os-x/

 - change folder where files go
 - change format (for example, to jpg, gif, tif, etc)
 - remove drop shadow
 - change file name (so it's not "Screen Shot")

Most of these start with
defaults write com.apple.screencapture 

be sure to do
killall SystemUIServer

for them to take effect.