Build your iPhone app mockup with Adobe Fireworks
http://blip.tv/building43/build-your-iphone-app-mockup-with-adobe-fireworksbu...
Luke Kilpatrick in a video talked about the process of iphone prototyping and why he uses Adobe Fireworks.
In 1-2 hours time, anyone can piece things together to show and discuss with anyone. You will find out lots more in this video.

