I installed this Mac Mini setup a year or two ago after stumbling upon Bugbyte's tutorial. I had been meaning to post it on the forum, but never got around to it. Well I just recently had to sell the car and took the system out, so I guess now is a good time to share it. I wish I had more photos of it.
Mac Mini Core 2 Duo
CarNetix P1900
In-Dash 7" Touchscreen K301 Monitor
Pioneer 600W GM-6300F Amplifier

And here's a video of it in action. I used my cell phone to record, which explains the quality.

::EDIT:: I forgot to mention everything is for sale except for the Mini on eBay.