Interfacer - Collection of more than 200+ free design resources
Sketch Repo - Collection of resources for anyone who uses Sketch
Facebook Design Resources - A collection of free resources made by designers at Facebook
Charts by ls.graphics - The most comprehensive collection of charts for Sketch
Freebiesbug - Collection of the best free web design resources.
Gmail Add-on Design Kit - A simple Sketch library to speed up Gmail Add-on designs