Anima App - Design, get feedback, convert to code, publish, iterate.
UXpin - Design is really about solving problems. UXPin is the UX Design Platform that gets that right.
Sketch Repo - Collection of resources for anyone who uses Sketch
Auto-Layout for Sketch - Responsive design for Sketch
Figma Auto Layout - Design more, resize less
Figma - Team-based interface design, Figma lets you collaborate on designs in real time.