Right now I'm putting together plans to mount an EeePC in my 2002 mustang and remove the screen to mount it on my head unit. Rather than buy a new head set I plan to just remove all the buttons and beveling from the head set and attach the 7" screen (w/ a touchscreen film) to the front of the unit. The audio will be run from the computer's audio jack to an AUX input on the back of the head unit. I plan to add bluetooth, GPS and WAN support to the laptop and write my own software interface. Estimated cost is less than $400
Another idea I've been toying with is using a micro-projector to overlay information such as a GPS map on the windshield. I'm just trying to brainstorm a way to project information without blinding oncoming traffic or skewing the image too much.
Any suggestions or ideas will be appreciated.