Anima App - Design, get feedback, convert to code, publish, iterate.
Now UI Kit - A beautiful Bootstrap 4 UI kit. Yours free.
Sketch Repo - Collection of resources for anyone who uses Sketch
Landing UI Kit - Handcrafted UI components for landing pages
Figma - Team-based interface design, Figma lets you collaborate on designs in real time.
Bots UI Kit - Fully customizable Sketch UI Kit for Messenger Platform