I agree with Punki, take a long walk along the lakefront. I usually walk from the area around the Shed Aquarium up to the Navy Pier. While most of the stuff inside the Navy Pier is tackey-touristy they do have some good restaurants. Also on weekends there are usually a few bands playing- and nothing beats having an ice cold beer while sitting on the Pier with the lake in front of you and the Chicago skyline behind listening to some classic rock & roll!
While in Chicago I usually stay at the Hyatt Printers Row, it is smaller and nearer my Chicago office. The best rooms are the '24' as in 424, 524, 624. They are larger corner room, with a VCR & most important, a view of the Lake. Mind you, it is just a sliver-view, but a view none the less. The restaurant there is first rate--kind of Frank Lloyd Wright inspired & great food. Also there is a good pizza place across the street- Edwardo's for take out when you want to just pig out in your room & watch TV.