Android Nougat GUI - Free fully customizable Android UI Kit for Sketch
Tetrisly - Starter kit for design systems and wireframes builder (Sketch/Figma)
Contra Wireframe Kit - Open source wireframe kit for design and prototyping ๐
Framer - ๐ฅ Design real websites right on the canvas.
Epic Pxls - UI kits, icons, templates, mockups and more, free
Flawwwless ui - Simplified open source React.js components library ๐