If you're into kickboxing, karate and traditional martial arts this is a great place to train. OMS is very clean with decent changing rooms and a big training mat. It's conveniently located off college ave with good access from highway 41. Check it out if you like traditional martial arts. You can always tell, they have a big glass window in front for everyone to watch!
If you want to really learn how to kick some butt take up Brazilian Jiu Jitsu at the Fox Valley Grappling Club run by Bill Krieg. Check out their website at www.foxvalleygrapplingclub.com. Stop in and say hello, the first two weeks are free!