I heard about OSM in summer 2008 and was fascinated from the beginning.
Unfortunately I dont own any GPS device, so that I cannot contribute with own tracks yet.
Since I am a biker, I am really dreaming about having a device which alows me to track on the bike and could maybe in the same time serve as a navigation system. And since I am studying mechatronics, it should be something self-engineered ;-)
So far I thought about the following components:
- Controller: Something based on Atmel AT32 µC like e. g. NGW100 or ICnova/Grasshopper. There is a Linux kernel available for this controller.
- GPS: Antaris Chips are said to be the most accurate on the marked today ... 
- Cam & Microphone: On the bike no hands free to take notes, so there should be a possibility to record voice and also have imaging. For the cam a simple webcam (Ethernet or USB) should do. For voice recording best would be some in-helmet bluetooth-device like this one.
- Display: An LCD would not be too bad. To adjust the camera, for setup and of course for the navi.
At the moment I am lacking time and money ... but as I said, this is what I would like to have! (contributors welcome)