Dedicated prototyping, storyboarding, and simulation tools let you quick mock up screen prototypes, storyboards, and in some cases even interactive simulations. You can use Microsoft Visio or most of the other Diagramming applications for this, but the dedicated tools are often easier to use and highly tailored for the interface design process. And as I said, some like iRise will even let you create an interactive simulation for your potential users to interact with.
- Balsamiq Mockups
- iRise (commercial prototyping, wireframes, and simulations)
- Pencil (free and open-source)
- Visual Prototype (a free [for now] version of the mock-up and prototyping tools that are part of the TopTeam Analyst requirements management software)
- Indigo Studio – From Infragistics this is a commercial tool for Storyboarding, Wireframing, and Prototyping all in one. Supports design of desktop, web, and mobile applications.