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