AutoIt Windows Screenshooter is a small and easy to use application that will help you take screenshots of any visible window and even from websites. It is a freeware screen capture application that's well-designed, portable, light on system resources and straightforward.
Here is a screenshot to illustrate the features and user interface of this application:
PicPick
WinCam
SmartCapture
HyperSnap
Snagit