Not too many choices at RIR for camping in a designated type of campground. But home owners surrounding the track turn their yards into mini campgrounds all arond the track, stuffing as many RV's into the back yard as possible, then filling the front yard up with more of them. It's kind of an odd sight to see, but I've done it from the same lady's backyard every year for many many years. There are also a couple of places along Meadowbrook Road like the Flea Market that provide camping space too. There was one Church across from the service entrance that used to charge $200 for the weekend, we only pay $30 per night to this lady we stay it...
The closest commerical campground would probably be the Amerikamp in Ashland, or Pocahontas State Park south of the city, both likely fully booked for race weekends and much too far from the track to avoid commuting. You best bet is to drive down Meadowbrick Road or Laburnam Ave day or so before the race, people wanting to make money renting yard space will be out there waving you in as you roll along down the street. Good luck...