Well, I found this nice video someone put together for their cinematography class project. It does an excellent job of describing the sport, who participates, what age groups, what type of cars, some basic rules, and quality footage of the events.
Enjoy... and if you like what you see, check out www.scca.com for more information on SOLO racing.
Sea of Cones : A Documentary About Autocross from Stephen Chiang on Vimeo.
( http://vimeo.com/12067348 )
Finally as an excellent follow up to the documentary, here is online tutorial that walks you through the basics :
http://www.wtfstables.com/rmsoloschool/