Sketch Talk - A community for Sketch users of all skill levels
Anima App - Design, get feedback, convert to code, publish, iterate.
SketchCasts - A weekly screencast, all about how to use Sketch
Sketch Repo - Collection of resources for anyone who uses Sketch
Sketch 101 by Designlab - Learn Sketch in this free course w/ downloadable templates
Git Sketch Plugin - Version control for designers