I bought a motorcycle mount for my iPhone last week and it came in yesterday. I had also bought the G-maps navigation app for the phone so I could use the iPhone for my navigation, phone & iPod.
I played with the mount on the handlebars for a long time but couldn't get the angle correct so I switched to the windshield mount and it worked out really well...I think. The navigation works great on it so far.
This weekend, I plan to tap into the navigation power port on the front of the bike and put in a marine cigarette lighter outlet so I can power the iPhone while in use as well as any other toys I add later. Then it will just come down to getting a bluetooth helmet and I'll be all set.
I wanted to start this thread and document the progress as I go so anyone other iPhone user may save some time if they want to recreate what I'm doing.