Anima App - Design, get feedback, convert to code, publish, iterate.
One Click Test - Tool for quickly testing your design layout in one click.
Sketch Repo - Collection of resources for anyone who uses Sketch
XPRS - Free website builder - making web design like Lego™. No code
Auto-Layout for Sketch - Responsive design for Sketch
Dimensions Toolkit - Chrome Extension for designers to test responsive websites.