Brakertech

Instantshot is by far my favorite screen capture program for the Mac.  It sits in your toolbar and you can have captures auto-save to the folder of your choice (I generally have them save to my dropbox so the screenshots are synced to the dropbox instance on my PC).

Below is an explanation of the program taken from the InstantShot homepage:

What are the features of InstantShot! ?

InstantShot! offers classical screenshot functionality for capturing the whole screen, a portion of it or a window and also the option to make timed screenshots or to make delayed captures over time. It offers a wide range of preferences and options to fit everyone’s needs.