What type of riding are you looking to do? Motocross? Woods/trails?
Lincoln Trail in Casey, IL, as mentioned above has it all - and you can ride every day if you wanted to for real cheap.
www.ltmoffroad.com
Another track favorite of mine is Planet Extreme in Mason, IL, about 30 minutes south-west of Casey. Motocross track and night stadium track.
www.planet-x-treme.com I think they also have a good membership deal like Casey.
Then if you wanted to travel a little, there are several practice and/or race tracks within a few hours.
IL: Taylorville, Joliet, Walnut, Galesburg, Hoopeston, Nashville, Salem, Peoria, Ottawa, Mendota, Wedron, Coal Valley, Byron, Hopkins Park, Waterman, Astoria, Rushville, Marion, Du Quoin, Belleville, Fosterburg and
IN: Rossville, Lafyette, Wabash, Hortonville, Winamac, Attica, Cayuga, Valparaiso, Rochester, Akron, Anderson, Linton, Mitchell, North Webster, Butler, Uniontown, La Otto, Charlestown....... just to give you an idea.