Look at a map, pick some random small town (perhaps inbetween two cities you're visiting) and go there. Try the local food, go to the local bar, visit the library talk to the people and ask if there's anywhere in town that's worth taking a look at.

When I travelled New England some of the best times I had were in small towns that I got to almost by accident. I've made some friends I still talk to almost 3 years later just from one overnight stay.

Anyway, have a fantastic time whatever you decide to do!