For the last few months, I've been using Hotgloo for wireframing. We're working on a new development project and now needed a collaborative flowcharting solution. I did some searches online for visio alternatives and found LucidChart.
Aside from an incredible interface, the tool works on iPad and also integrates with Google Apps… two great additional features for me, personally! If you've ever used Visio (which I love but simply can't afford to license), you'll find LucidChart simple to use. You can also import Visio diagrams with the professional edition ($9.95 per month!). Here it is in action on the iPad version:
The application is so robust that I am going to utilize it for wireframing as well. There are a few tutorials on the LucidChart Youtube channel on using the tool for wireframing and I can use it for many more projects than the HotGloo pricing allows. They also offer the ability to add organization charts, iPhone mockups, UML diagrams, network diagrams, mind maps, site maps, Venn diagrams and more.
Use my referral link and you can test out all of the premium features of LucidChart free for one month!