Mobile Chat Kit - UI kits & sample apps for building in-app mobile chat
Sketch Repo - Collection of resources for anyone who uses Sketch
Ambient Design - Ambient is a mobile app design market where you can get unique mobile UI kits.
Charts by ls.graphics - The most comprehensive collection of charts for Sketch
iOS Design Kit - The newest library of native iOS templates
Gmail Add-on Design Kit - A simple Sketch library to speed up Gmail Add-on designs