I was just checking out this excellent piece by Cliff Atkinson about how to use power point and screen capture to quickly illustrate your blog posts with images.

I just downloaded the tool he uses for screen capture - SnagIt, and after using it for just 5 minutes I'm already getting misty-eyed thinking about how this may change my life (I think I need a tissue).

I grabbed the image below by using the region capture feature within SnagIt and then adding my own text.  Took a total of 3 minutes (and half of that is because I was playing with all of the cool features).

If you do any kind of product documentation, diagramming, screen shot annotation, etc, this tool is a must have!!