I'm TAing an AI class and we're trying to put together a car simulator for the students to use for an assignment that involves training a computer to control a car. We want the assignment to be relatively fun with a nice reward at the end so even though graphics aren't critical to the purpose of the assignment we'd like to have a 3D rendering of a car with some nice spark or flame effects for the skid. Does anyone have any suggestions for where I could get some car models? Does anyone happen to know of any open source racing games? I don't have any trouble with doing a bit of coding myself and we already have the dynamics down, we're just looking to put a bit nicer of a front end on it than we have so far.

http://torcs.sourceforge.net/

In my fuzzy logic course, everyone wrote a car for Torcs and we raced them at the end of the semester. It worked really well.