Invision - Prototyping and collaboration for design teams
LucidChart - LucidChart is the missing link in online productivity suites. LucidChart allows users to create, collaborate on, and publish attractive flowcharts and other diagrams from a web browser.
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.
draw.io - Online diagramming application
Zeplin - Collaboration app for UI designers & frontend developers
Visio - Simplify and communicate complex information using data-linked diagrams.