There is a Dickeyville Grotto in Dickeyville, WI that is pretty neat. It has a religious theme, but the story behind it is pretty cool. It is made of mostly small colored stones, fossils, shells and bits of glass. I saw it several years ago and loved it. There is also House on the Rock in Spring Green, WI, and some other attractions in out of the way places. Your best bet is to stick to side roads and avoid the Interstates. I had a truck driver tell me about the largest Cypress tree in Cypress, IL, near a place called Cache Creek. The tree is supposed to be a monster and they have built a walkway out to it so you can walk all the way around the tree.
Another place I like isn’t an attraction, but it is a local piece of geological history. The area of SW Wisconsin, NE Iowa, and the extreme portion of NW IL is called the Driftless Region. It is an area missed by the last Ice Age and contains a range of mountains that were once under a huge inland sea. It is one of my favorite places to visit and driving down the small winding roads and just taking in the scenery between the occasional small towns is fun. You can find some neat little shops in these towns, if you look carefully. It is a beautiful place and best of all, not too far away.
There is also a really neat haunted attraction in Mt. Carroll IL called Raven’s Grin that is pretty neat to visit, and it is open nearly year round, 300 daysd a year, I think. Going there around Halloween is pretty much impossible, due to the heavy traffic.