Last month Russ Fustino did a presentation in Portland, ME where he showed a little tool to grab areas of the screen. I looked on his blog, but could not find a link to this particular tool, but a little Googling did the trick.

Screen Grab Pro is a very nice (FREE) tool from Traction Software that allows you to easily grab a region on the screen and save it as a file, or paste it in a Word document.

Update: Windows Vista also offers a build in tool called 'Snipping Tool'. On some machines this tool does not get installed by default, read more on the Snipping Tool here (thanks Marcel!).