MLB : Its the White Sox, and whatever team is playing the Cubs. I do like the Nats a lot, which is why I hang out here.
NFL: Bears, of course. No matter what anyone argues about the Cubs and Sox, Chicago is really a Bears town. But I also like the Arizona Cardinals (I will always feel linked to Chicago's "other" southside team. The Cardinals were originally in Chicago, and played thier games at Comiskey Park).
NBA: Bulls (but I am much more of a bandwagon fan of the NBA, and haven't really closely follwed basketball since the Michael Jordan years)
NCAA Basketball: Illinois, and I'll watch/follow just about any big 10 team.
NCAA Football: Not really a follower of a particular team, but I pull for whoever is playing Notre Dame.
NHL: I hang my head in shame when I admit it, but yes, its the Blackhawks.