Source Wireframe Kit - Library of 537 blocks for desktop and mobile prototyping
Contra Wireframe Kit - Open source wireframe kit for design and prototyping 🚀
Platforma - Wireframe library of layouts and UI elements
Craftwork - A collection of User Interface resources made by Craftwork
Invision - Prototyping and collaboration for design teams
Rodman Mobile UI Kit - Premium colorful iOS templates designed for Sketch App