It's kind of hard to pass up Boston, since it's right on the way. New England Aquarium, Freedom Trail, Fanueil Hall and marketplace, Swan boats, a Sox game if you can get tickets, good restaurants ....
You don't have to stay long, but a 2-night stop with a full day to putter around would be nice. Or longer if you like it.

Anonymous wrote:Thanks--I'm Op. I think both cities and nature are good. Not much interest in a beach (would just go to eastern shore for that) but kitschy historical beach stuff might be fun. Any more ideas? Keep them coming!

Then I think Portland and Acadia will be great for you. If you want to hit larger cities on the way, you could, but I'd personally avoid the hassle.

Burlington, VT is a really nice small 'city', but it's not close to Acadia.