Brand.ai - Create a style guide & integrate with Sketch, Slack, & Gulp
Anima App - Design, get feedback, convert to code, publish, iterate.
Sketch Styler - Sets the most similar style to unstyled layers automatically
Sketch Repo - Collection of resources for anyone who uses Sketch
Figma - Team-based interface design, Figma lets you collaborate on designs in real time.
Frames for Sketch - Create awesome websites & apps using powerful design system