If there'd been more time ...
There was too much conference! The only free time was Tuesday afternoon when I went to the Art Institute. So, I regretted not visiting and photographing these:

The Field Museum
The Picasso Sculpture at the Daley Center
The Sears Tower from which you can see 4 states (Illinois, Indiana, Michigan, and Wisconsin)
The Hancock Tower
Greektown on the west side of Chicago and especially the legendary Greek Islands restaurant (Opaah!)
Oak Park, a suburb to the to the west, to see homes designed by Frank Lloyd Wright
Marshall Field's
Wrigley Field, the other Mecca, for a REAL, old-fashioned, baseball game on real grass, with people watching for free from the rooftops of the apartment buildings across the street, all watching the Cubs lose again. If you can stand some slow loading pages, here's a virtual tour of Wrigley Field.
The night before I left I found out about a pair of photographic exhibitions at the Chicago Historical Society: work of photojournalists who died in Vietnam and Harry Benson's photographs of The Beatles.
The Oriental Institute Museum is also very nice and The Museum of Science and Industry is a lot of fun.
And this doesn't even get into clubs and bars and restaurants and funky neighborhoods and art galleries and shops and ...