You can hardly swing a dead cat in Wisconsin without hitting a few Frank Lloyd Wright buildings. Visit
http://www.wrightinwisconsin.org/ or
http://architecture.about.com/library/bl-wright-list.htm#Wisconsin for listings.
The problem with a lot of FLW houses is that people, you know,
live there. Now, I'd like to believe that the people who reside in FLW houses are afficionados both of modern architecture and of spoken-word poetry, and would gladly welcome you into their homes for a tour and quite possibly a home-cooked meal. But you can't count on that sort of thing, even from friendly Midwesterly-type people.
So consider government buildings, museums, and churches.
- The FLW Unitarian Church in Madison is open all Spring, Summer, and Fall
except for the first week in August. Probably so they can get watch poetry, right?
- The Monona Terrace Convention Center is, among other things, the big photo on
http://www.nps2008.com.
- Taliesin (FLW's home) is in Spring Green, about 30 miles west of Madison. Tours all the time.
- Annunciation Greek Orthodox Church is in Milwaukee. I wrote a report on it in high school and it is totally kick-ass (the church) (although the report wasn't bad, either). They're not usually big on visitors, but if you get Simone liquored up at the Safe House, she'll probably give you the password to Annunciation Church

Or am I the only architecture geek in the place?