Greenshot is a light-weight screenshot software tool for Windows with the following key features: Quickly create screenshots of a selected region, window or fullscreen; you can even capture complete (scrolling) web pages from Internet Explorer. It is a free and open source screen capture application that's feature-rich, advanced, well-designed and comprehensive.
Here are some screenshots to illustrate the features and user interface of this application:
PicPick
WinCam
SmartCapture
HyperSnap
Snagit