This LEGO car features a working seven-speed gearbox, including reverse gear, and is remote controlled. That's just sick!
More pictures and movies can be found over here. If LEGO ever packages this in a box I'll definitely buy it. :-)
There is a blog to go with this, but not in a language I speak.
Wish I could build something like that. I think I could handle the software and the cabinet, but the controls, wiring and arduino-magic are beyond me. My dad always said I should take an electronics course, but I never really considered it. Though I doubt that he was thinking about using it for stuff like this... If this was on the curriculum I would have signed up in a heartbeat. :-)