Raspberry Pi ARM board
I was linked to this elsewhere and figured I'd share it with the folks here as it has huge potential in the CarPC area as a VERY inexpensive CarPC base that is powerful enough for pretty much all mainstream applications given a custom built CarPC linux distro is developed for it.
Unfortunately I am not at my main computer at the moment so can't repost the details that I want, but their site has pretty much all you need. In essence the hardware is basically your average smartphone base with some extra bells and whistles minus the user interface options, all for $25 for the A model or $35 for the B model. 700MHZ ARM11 CPU (likely overclockable I'd imagine), Broadcom VideoCore IV GPU which has OpenGL ES 2.0 support and can decode 1080p30 high profile H264 video, 256MB ram for the B model, 128 for the A (Mind you with a dedicated custom built linux distrobution, 256MB should be plenty), 2 USB ports, Composite Video, HDMI, and DSI/LVDS video outputs, and GPIO pins with an expected Fusion Brain-like daughterboard coming soon. All with a very modest power rating of around 700ma to maybe 1A max at 5V.
But they key bit is it is powerful and customizable smartphone based hardware minus the OS restriction to the point you can write your own OS for it built for the CarPC environment with a custom frontend and do it all in a tiny footprint and such low power requirements you could likely leave it always powered without a serious drain on the battery.