Here are some threads I used when planning my trip:
http://texags.com/main/forum.reply.asp?topic_id=1422074&forum_id=54phttp://texags.com/main/forum.reply.asp?topic_id=1398850&forum_id=54http://texags.com/main/forum.reply.asp?topic_id=1490152&forum_id=54Pizza - Giordanos & Gino's East are good picks for deep dish. If you desire, there are also pizza tours in the city. We went on
this pizza tour which we both really enjoyed.
Most people told me Navy Pier is way overrated, so we skipped that.
My wife liked the time we spent walking down the Magnificent Mile, shopping and such. We spent a few hours shopping and looking, then went up to the 94th Floor in Hancock Tower before dinner, it was a relaxing evening.
Millennium Park is a must do, you won't miss the iconic bean. They had ice skating when we were there which was fun.
The Field Museum, Soldier Field, the Aquarium and Planetarium are all grouped together. We only went to the Field Museum and took a few pictures outside of Soldier Field. It was time well spent.
We went on the Architecture Tour (by bus because it was winter). My wife thoroughly enjoyed it.
Chicago Cultural Center is a free site with decent exhibits.
We took the Red Line to Wrigleyville just to check out the area, pubs surround the ballpark. On the way back, we also stopped at Armitage for a little bit more shopping. Vosges has a chocolate store there.
We went to the Art Institute on a free day. It's huge. If you like art, I'm sure you could spend a whole day there.
This site lists free days for area attractionsHeard from others that the Museum of Science and Industry was really good. It's right down the road from University of Chicago who has a beautiful campus (we saw this as part of the architecture tour)
Al's #1 Beef is a popular and excellent place to grab a sandwich. I really liked Ni9e for upscale dining. MK Restaurant is pretty good. Cafe Spiagga was a complete bust in my opinion, hated it.
Andy's Jazz Club and Rockit are right next to each other. People raved about Rockit, but we did not go. I loved Andy's though.
I loved Blue Chicago for blues. There's a cool Irish Pub across the street called Celtic Crossing.
Stay downtown, take the very efficient train system during the day (you can get multiday passes) and take taxis at night. We didn't even have to get a car.