Flowkit - Sketch library for user flows/content maps/annotations
Sketch Talk - A community for Sketch users of all skill levels
Crystal: Sketch Mirror for Android - Crystal: Sketch Mirror for Android is an application that is designed for viewing your sketch designs in real-time, navigate prototypes and download content related to the sketches for offline viewing.
SketchCasts - A weekly screencast, all about how to use Sketch
Figma Mirror - Figma Mirror is an application that covers top trending designing or sketching ideas making your teamwork in a single environment and design better products from start to finish.
GoRails - Ruby on Rails screencasts for Web Developers