Here are some of my favorite attractions on the 'inland' road back from Maine to New York. Note that everything that follows are direct quotes from previous posts that I found using the Search Function above.
As you head out through Massachusetts, there's Old Sturbridge Village a 'living history' recreation of a 19th century town. You can then head on north a bit and use the Mohawk Trail through the Berkshires.
I have toured the Mark Twain House that Mass Tim suggested and found it quite fascinating. Two smaller scale (and lesser known) things you might also consider, depending on your predilections are Dinosaur State Park where you can make plaster casts of real dino foot prints (Buy your own plaster of paris at a local hardware store. Be on the lookout for this sign) and the historic Rocky Hill-Glastonbury ferry. Both of these sites are just southeast of Hartford.