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
Craftwork - A collection of User Interface resources made by Craftwork
Figma Auto Layout - Design more, resize less
Streamline - Streamline is a web-based vacation rental software that manages vacation rental properties with flipkey integration, online booking, lead management, credit card processing, etc.