My favorite museums are the Art Institute and the Shedd Aquarium, followed by the Field Museum of Natural History. If you like German food, eat at Bergdoffs (I think that's it). Great food, beer and Manhattans.

Nedra

If you want authentic deep dish Chicago style pizza, I would suggest Pizzario Uno (the original site is great). Pizzaria Duo is the same thing, I think, just their second location right around the corner.

JanMD suggested an architectural boat tour. That was by far the best way to see and understand Chicago, from Lake Michigan. There are several different types of boat tours that emphasize different aspects of the city, such as architecture, history, etc. Definitely worth the time and $$.

We stayed down near the Shedd and Natural History Museum and right across from Grant Park. There was a Jazz and Blues festival going on the whole time we were in town, so we headed down there each night. It was great, and I think that there are festivals almost every weekend in Grant Park all summer long. Ravenia Music Festival is quite a bit north, but also very good.

I'm not much of a shopper, so we didn't go to any of the high end fancy shopping (but we did take pictures of PETA in front of Norstrom's protesting fur coats).

I'm jealous--have fun!!