Platforma - Wireframe library of layouts and UI elements
Contra Wireframe Kit - Open source wireframe kit for design and prototyping 🚀
Form Wireframe Kit by InVision - A free wireframe kit from InVision
Craftwork - A collection of User Interface resources made by Craftwork
Apple Watch UI Kit - Quickly create Apple Watch app prototypes
Method Wireframe Kit - Find your method of being incredibly fast in prototyping.