Craftwork - A collection of User Interface resources made by Craftwork
UXpin - Design is really about solving problems. UXPin is the UX Design Platform that gets that right.
Source Wireframe Kit - Library of 537 blocks for desktop and mobile prototyping
Auto-Layout for Sketch - Responsive design for Sketch
Contra Wireframe Kit - Open source wireframe kit for design and prototyping 🚀
Figma Auto Layout - Design more, resize less