Nokia Tablets - some software for cars
I'm developing a GPS and OBD-II backend (which already works with the proprietary data on my Harley, which is sadly in storage now until the snow goes away).
The Nokia n810 units are around $400, and feature an 800x480 transflective (sunlight readable) screen (the colors lose saturation but it is quite readable).
There is a parallel project "Carman" which is fancier.
Most use any Elm327 based scanner with a bluetooth link including the $60 one from deal extreme, but I prefer the ObdPros module:
(which has extended modes, like wake-up-in-monitor-mode I use on my Harley).
Most of these projects can be found with descriptions and comments on Internet Tablet Talk
With links to project pages.
I just added experimental Valentine V1 support and have the data going through an aircable http://aircable.net/mini-os.html module with about $10 of radioshack parts (phone cord, 2*4k, 10k, 2n3904 - aircable powered via phone cord).
I haven't seen much discussion here lately so I thought I would mention it. The minigpsd program is Linux centric, not Nokia centric and logs to KML (and includes as XML comments all the OBD traffic and every NMEA sentence). The Nokia has a built-in GPS, and I use that in parallel with my 10Hz GPS, as I do on my laptop - my programs work on any Linux system.