You can use basic keyboard shortcuts to capture screenshots. You can use 'Grab', but this is much quicker.
Listen to the Podcast for instructions!
Hold down COMMAND+SHIFT+3
and it will grab the whole desktop, whatever you can see.
Hold Down COMMAND+SHIFT+4
and it will present you with a cross hair, and you can drag and click a cross hair over the area you want to capture.
You can also use COMMAND+SHIFT+4 and then press the SPACEBAR
this will bring up a camera icon (can't see in this image though..sorry)
that you can move to select a particular open window -- Very Useful.