The WDCR autocross events are some of the largest in the country. They are a little hard to get into (you have to sit at your computer when registration opens and enter - they fill up in about 15 minutes or so.). They allow spectating and the next one is on 6/17.
If you are willing to drive a little further, on July 15th there is going to be an autocross in Aberdeen MD at Cal Ripken Stadium. Held by:
http://www.autocrossersinc.org/ There is a small chance that I may be here - my wife's due date is the 22nd and I may be on restricted travel.