Where to Go?--Jan 16th

I have a question for all you Chicago-forumers. My friends and I normally take a 4-5 weekend trips to Chicago during the year, and I'm heading there for the weekend of January 16th. I grew up spending a lot of time in Chicago, living in Madison and Milwaukee, so I'm pretty familar with the normal things to do in Chicago. I'm staying at the Hyatt Regency on Wacker (always have, even through the very ugly recent remodel) and I'm really looking for the things to do to experience the true city. My friends and I have always been interested in finding the interesting neighborhoods, eateries, nightclubs and so on, that represent the area they're in. We're all about experiencing the culture of the city the way a resident would (we do this everywhere we go) So where should I go? I hate getting the car out of valet so we're talking strictly by train, bus, cab (as long as its not a ridiculous distance). Where should a group of 21 year olds go to experience Chicago?>