Requires jailbreak (?)
A web based micro-forum for the iPhone microforum
A hosted, threaded forum for the iPhone.
Built with iUI and Rails in 2 hours.
My first app with iUI -- for more info on the framework, visit http://code.google.com/p/iui/
Note -- you dont have to be a registered beta user to use this. You don't even need an iPhone. Just resize your FireFox or Safari window, and pretend!