Rodman Mobile UI Kit - Premium colorful iOS templates designed for Sketch App
UX Flow Wireframe Prototyping System - Create beautiful user flows prototypes for your next project
Landing UI Kit - Handcrafted UI components for landing pages
draw.io - Online diagramming application
iOS Design Kit - The newest library of native iOS templates
yEd - yEd is a free desktop application to quickly create, import, edit, and automatically arrange diagrams. It runs on Windows, Mac OS X, and Unix/Linux.