Design Systems Handbook by DesignBetter.Co - Your guide to design systems best practices
Anima App - Design, get feedback, convert to code, publish, iterate.
The DesignOps Handbook by InVision - Guide to understanding how DesignOps help design teams scale
Sketch Repo - Collection of resources for anyone who uses Sketch
Design Principles - An open source repository of design principles and methods
Figma - Team-based interface design, Figma lets you collaborate on designs in real time.