SketchCasts - A weekly screencast, all about how to use Sketch
Mockuuups Studio - Fast and easy way to create product mockups on macOS, Windows and Linux.
Base UI Sketch Framework - Huge set of everything you need to design and prototype
Mockup Generator - Create attractive product screenshots with just a few clicks
Framer - 🔥 Design real websites right on the canvas.
shotsnapp - Create beautiful device mockup presentation