Source Wireframe Kit - Library of 537 blocks for desktop and mobile prototyping
Fae - Design in Figma, publish as a React component via npm
Contra Wireframe Kit - Open source wireframe kit for design and prototyping 🚀
Wannathis - 3d illustrations and freebies
UX Wireframe Kits - Simple, beautiful wireframe kits for Sketch & Illustrator
UI Flow Cards - Construct web pages with ease, using cards