I noticed theres another thread asking the same thing =) either one is fine to put your suggestions

check out the MCA (museum of contemporary art)
Shedd Aquarium is cool/expensive
take a boat tour (if they still do them at this time of year), best way to get a sense of the city layout, they're relatively cheap too

contemporary bldgs:

Contemporaine- Perkins + Will [516 N. Wells]
Thompson Center- Murphy/Jahn [Dearborn & Randolph?] for some reason i'm one of the few people who likes this bldg.
Soldier Field
Skybridge- Perkins + Will [1 North Halsted]
....

Crown Fountain in Millennium Park.

http://www.millenniumpark.org/artandarchitecture/crown_fountain.html

Check here, they are some award winning buildings done by last year:

http://www.aiachicago.org/special_features/2005DEA/

If you have see some buildings you really like, you might just rent a car and drive to there.

Does everyone visit Chicago? Where's the 'off to Topeka - what to see' thread?

oh man... topeka

when i was little... we played a soccer tourn there every year... they have some of the most incredible grain silos

crown fountain/prizker pavillion at millenium park

stateway gardens...it's beautiful this time of year.