ProtoPie - ProtoPie is the easiest tool used to turn your UI/UX design ideas into highly interactive prototypes for mobile, desktop, web, all the way to IoT.
Platforma - Wireframe library of layouts and UI elements
Framer - 🔥 Design real websites right on the canvas.
Source Wireframe Kit - Library of 537 blocks for desktop and mobile prototyping
Invision - Prototyping and collaboration for design teams
Contra Wireframe Kit - Open source wireframe kit for design and prototyping 🚀