Greenshot is a free open source screenshot utility.

Lightshot is the fastest way to take a customizable screenshot. Simple interface, nothing useless and light weight.

Gyazo is an open source screenshot program for Windows, Mac OS X and Linux.

Grabilla is a software that takes a screenshot of the user's computer screen and uploads it to the Web, FTP, computer or copy to clipboard.

FastStone Capture is a powerful, lightweight, yet full-featured screen capture tool and screen video recorder.

FireShot makes full web page screenshots.

DuckLink Screen Capture is a screen capture software.

Easy Screen Capture and Annotation is a screenshot tool.