iOS Design Kit - The newest library of native iOS templates
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.
Sketch Repo - Collection of resources for anyone who uses 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.
SketchApp.rocks - Index of all awesome things related to Sketch.
Flowkit - Sketch library for user flows/content maps/annotations