Matt, depending on what part of the city you are staying in, there are plenty of great spots. One thing you have to try is pizza. We have great places in the downtown area for both thin crust and deep-dish. Gino's East or Pizzaria Due are both downtown. Also just south of the Loop is Chinatown. Try The Junk in Chinatown. Lot's of great places, you can't go wrong!
Thanks a lot Chuck for the suggestions. I've been to Chicago before but felt a little overwhelmed by all the choices. I ended up eating at places like Ditka's but know that there have to be a lot of hidden gems. Hole in the wall type places that the average tourist wouldn't know about.