Platforma - Wireframe library of layouts and UI elements
Source Wireframe Kit - Library of 537 blocks for desktop and mobile prototyping
Contra Wireframe Kit - Open source wireframe kit for design and prototyping 🚀
Form Wireframe Kit by InVision - A free wireframe kit from InVision
Method Wireframe Kit - Find your method of being incredibly fast in prototyping.
Invision - Prototyping and collaboration for design teams