At my previous employer we upgraded to Windows Vista, and one of the neat features I liked about it was a tool called "Windows Snipping Tool".  It allowed you to take much more efficient screen shots of things.  But it wasn't available for my home PC which has XP Pro on it. 

So I went searching for a program to use on XP and I found http://www.windowclippings.com/  This is a really good program that allows me to take specific screen shots without having to open up an image editor to crop it.  Here is a sample screen shot, all I had to do to get this screen shot was hit the Print Screen button and right click the screen to crop or expand my selection, then double click the area I selected.  It spits out a PNG file (which you can change to a few other image formats) and due to my settings sticks the image in my clip board for easy pasting into a document or email.

The last great thing about this is its price... just $10!  While free is better you can't argue with $10.