Lucidchart

If you need a diagramming app and don’t like the expense and functionality of Visio, try Lucidchart

LucidChart

Lucidchart says:

Diagrams done right.
We have rethought and redesigned the entire diagramming process to make it as easy as possible. Draw flow charts,wireframes, mind maps, org charts, UML diagrams, and more with just a few clicks.

Wireframes & mockups
From static wireframes to rapid prototypes, web developers can do it all with Lucidchart’s wireframe tool. Collaborate with your client and design team in real-time to cut down on iterations.