ScreenChopper is an application that facilitates taking snapshot of your computer screen. You can take the shot by only one keystroke at any time and an immediate snapshot manipulation is provided for you to Chop off any part you want and to save it as a bitmap file. Also when the snapshot (or a part of it) is saved, you may ask the image being saved with a different size from actual one to get a stretched or resampled image to fit you need.
When ScreenChopper starts up, it stays in system tray of your computer. So you can make the program to run as your computer starts up since it does not take up your desktop space, and easily snapshot the screen at any time you like.