I would recommend you have a look at The Museum of Questionable Medical Devices in Minneapolis. The biggest kick was the phrenology machine. For a buck or so (I was there a long time ago.) you can have this device strapped on your head which measures your cranium and prints out your personality profile.

Any railroad buff will appreciate The Twin City Model Railroad Museum in St. Paul. I especially like the outstandingly realistic scenery.

I also recommend Forts Folle Avoine Historical Park, in Burnett County, Wisconsin. The tour guides there were excellent.

You may be able to find other interesting sites at Roadside America.