If you like Mexican food, check out Frontera Grill & Topolobampo (2 different restaurants in one place..one is a bit more expensive) at 445 N Clark St. GREAT food and margaritas that were featured in Playboy magazine (not that I read it..

..they had the article hanging up).
Forget the Cubs! Go to a Sox game! Wrigley does have a much better neighborhood but Sox tickets are much easier to get and the team is better.

Comiskey...uh...U.S. Cellular Park has gone through some renovations and is MUCH nicer than people like to believe. Not sure what dates you’ll be here, but tickets are half price on Mondays and Tuesdays (if you brink a pepsi can).
A good pizza place is Pequod’s on Webster & Clybourn. The crust has caramelized cheese and is fantastic. It’s a whole in the wall type of place, but if you’re looking for good food at a non-tourist place, go there.
Navy Pier is fun, as is the Shed Aquarium, Museum of Science & Industry. The Art Institute on Michigan Ave. shouldn’t be missed and is Free on Tuesdays!
I normally stay away from the bars on Rush & Division. If you’re in your early twenties and want to get crazy, those are good bars. There’s a place on Elm St. called The Hangge Uppe that’s pretty cool. Upstairs is your typical club, but downstairs they play older music and have albums plastered all over the walls. A fun, upbeat place. I used to frequent a place called Danny’s on Dickens St. It’s a house turned into a bar...kinda dark place...couches to sit on...they play great music, serve a good drink and have plenty of interesting people to look at. The Green Dolphin is a pricey restaurant & jazz club that’s also pretty cool. Good food and good music.
Peteloaf obviously knows what he’s talking about. Too Much Light, Uncle Fun, Music Box, Brew & View, etc. are all great places that us Chicagoans love.
Check out
http://chicago.citysearch.com for more info on these and other places. Enjoy your stay!