Clay Mockups - Free set of beautiful device mockups for your designs
Greenshot - Greenshot is a free and open source screenshot tool that allows annotation and highlighting using the built-in image editor.
Craftwork - A collection of User Interface resources made by Craftwork
ShareX - ShareX is a free and open source program that lets you capture or record any area of your screen...
AppLaunchpad - Create free beautiful screenshots for App store/Google play
LightShot - The fastest way to take a customizable screenshot.