UX Archive Animated - iOS apps animated user flows
UX Flow Wireframe Prototyping System - Create beautiful user flows prototypes for your next project
Page Flows - User flow design inspiration for mobile & desktop
draw.io - Online diagramming application
UI Patterns - Level up with interactive mobile design patterns
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.