Invision - Prototyping and collaboration for design teams
SmartDraw - Instead of starting with a blank screen, SmartDraw gives you the exact template you need.
Proto.io - Create fully-interactive high-fidelity prototypes in minutes that look and work exactly like your app should. Sign up for a free 15-day trial and get started.
Diagram Ring - Diagram Ring is an all in one universal level of diagram editor for DFDs, pie charts, bar charts, flow charts, class diagrams and much more.
Zeplin - Collaboration app for UI designers & frontend developers
GenMyModel - Industry Standards Compliance. Finally a tool which respects 100% of the UML 2. 5 standards to model your software, and BPMN 2 standards for your business process.