Greenshot - Greenshot is a free and open source screenshot tool that allows annotation and highlighting using the built-in image editor.

Imgur - Imgur is a free and simple image hosting service with image editing feature. Signup is optional.

ShareX - ShareX is a free and open source program that lets you capture or record any area of your screen...

LightShot - The fastest way to take a customizable screenshot.

CloudApp - CloudApp allows you to share images, links, music, videos and files. Here is how it works: choose a file, drag it to the menubar and let us take care of the rest.

Snagit - Screen Capture Software for Windows and Mac