Lightscreen is an easy-to-use program to save images of your screen. Includes customizable hotkeys and ability to capture a single window, a user specified region, or the full screen. Can then save with an optional delay to a variable quality JPG, PNG (high compression), BMP, or to the system clipboard to paste into a graphics application of your choice.
Cross platform with a client available for Linux and includes support for uploading to the Imgur image hosting service.
Alternatively, Lightscreen Portable is also available.
