SnapCrab is a nice and handy tool which provides different ways to capture snapshots from the desktop screen. It can be used to capture the whole screen, a specific window, or a specific area on the screen. You can choose a particular file format and file location in which you want to save your screenshots.
SnapCrab displays a magnifier window to precisely preview the captured area. It has a inbuilt color picker tool which picks different shades of colors from the screen and identifies their RGB values. Apart from that, it also lets you instantly post the screenshots to your Facebook and Twitter account.
It also allows you to directly open the screenshots with your default image editor. Moreover, it offers a great combination of tools and settings to enhance your screen capture experience.
SnapCrab : http://goo.gl/aOc4Y