Design Principles - An open source repository of design principles and methods

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

Facebook Design Resources - A collection of free resources made by designers at Facebook

Shutter - Shutter is a feature-rich screenshot program.

Facebook - Connect with friends, family and other people you know. Share photos and videos, send messages and get updates.

Snipping Tool - Use Snipping Tool to capture a screen shot, or snip, of any object on your screen, and then annotate, save, or share the image