I drive my Impreza in the Street Touring Street-Tire, STS, class.  I chose this one because it fit the mods I wanted to make to the car and I knew from past experience that CSP was just a very hard class.   The main competition is the Acura Integra GSR in this class though locally there are also Civics, a Maxda MX-6, a Ford Probe, a VW Golf, a Saturn, and a VW Jetta that have run along with a few other RS's.   Here's the STS class information for others interested in autocrossing their Impreza.

I've also done some track driving, check out the page for more information. 

What is it like to Autocross?

Autocross is a lot of fun while you are driving, it is also a lot of sitting around or shagging cones when you are not driving.  Is it worth several hours and $15 to get in basically 3 minutes of racing?  Right now I say "YES" because those three minutes are so fun and the people are just great.   Here's a RealVideo of my best run at the SCCA Regional #5 from inside the car, sorry for the poor image quality,  I created the movie with a low-bandwidth connection in mind.   The file is just over .5Mb in size and you'll need the RealVideo player from www.real.com.

This footage was shot with my Sony DV camcorder mounted on the harness bar  then captured, edited, and created with Pinnacle StudioDV.