Screenzy - A simple screenshot beautifier
Xnapper - Take beautiful screenshots instantly
Pika.style - A free tool to quickly convert screenshots into beautiful website and device mockups. You can create customizable images for App Store, Instagram, and more
Screen Guru - Take clean screenshots of any website
tweet.pics - Add a unique brand to your images to make them really pop on Twitter.
Supershots - Turn screenshots into supershots with gradient backgrounds