Bay City was nice and is just a little further away than that if you want to get to the Coast.
I'll second Indy for a fun weekend. St. Louis was also pretty cool.
We just went to Niagara. Did the tourist shit for 2 days, then went to Niagara on the Lake for 2 days. Rented a tandem bike and went to 10 wineries, that was a blast! You can even go spend some time in Toronto if you want some of the big city feel on that trip. We probably would have done that if we had a few more days.
Bay City Michigan was fun, but that was probably mostly because we accidentally went there on the county fair weekend and they had a cheap car race going on. You could take your own beer into the fair!
We are mulling around what to do for a long weekend at the end of July and may do the Michigan winery thing. Something over on Lake Michigan would be nice.
The Smokies is in that driving range. You can go drive Cherohala Skyway and Tail of the Dragon, do some hiking.
Chicago is always an option.