Design Principles - An open source repository of design principles and methods
Sketch Repo - Collection of resources for anyone who uses Sketch
Facebook Design Resources - A collection of free resources made by designers at Facebook
Anima App - Design, get feedback, convert to code, publish, iterate.
Facebook - Connect with friends, family and other people you know. Share photos and videos, send messages and get updates.
Figma - Team-based interface design, Figma lets you collaborate on designs in real time.