Somebody has built The Ultimate Linux Car PC:
I am throwing up this page because I have yet to see a decent LINUX based CarPC that shows the potential of what can be achieved if the effort is put forth. I have spent the last month or so tweaking the software as well as fabricating the LCD and controls to the point where I am satisfied with the result.
What I CAN do:
* Listen to music
* Watch videos/movies
* Control audio with steering wheel control. Since the audio is fed into the HU with a P.I.E adapter, the steering wheel is my “master” volume control.
* View Pictures in a slideshow
* Sniff wireless networks and plot them with GPS – I’ve plotted the APs I’ve found, and integrated it with Google’s Map API, check it out.
* Download and view local Weather info, including 3 day forcast and doplar radar
* Browse the web with Firefox
* Connect to my cell phone with bluetooth, and connect to Verizon’s EVDO network
* Stream DirecTV from my house. < - This is my FAVORITE - Basically I am using ssh keys and scripts to connect to my MythTV box at home, change to the channel I want, start vlc, which does on the fly transcoding of the signal, then connects to it from my CarPC. The result is a list of channels in my videos menu, I select the channel I want, and it all happens auto-magically.
* Remote start my car, and connect to it from inside my house. I can SSH in, and transfer files without even getting off my couch 
What I CAN'T do:
* Turn-by-Turn navigation. There just isn't anything out there for Linux.
One word: SWEET!!!
Amazing! I would Like further info & details on the construction of this marvel.