I did this trip several times. Once up I-95. Ok, not great. Once through MA and CT, I was stopping to visit friends. It's the long way to Maine but a nice ride. My preference is north on I-87 in NY then Rt 6 across Vermont and New Hampshire.
Ben & Jerry's is in Vermont. Go to the Auto Road in New Hampshire. Wonderful ride up a gravel road to the top of Mt Washington, 6288 feet up, takes about a half hour. I have ridden up this twice on my '84 Venture Royale. I hike up once, also, taking the Cog Railroad back down. Oh, there's a post office at the top of the mountain. And remember, when you see fog... it's really a cloud.
If you can, stop at the The Littleton Diner. It's a quaint little diner that serves a great breakfast.
In Maine, I camped at Quiet Side Campground near Bass Harbor (they have cabins, too). In Seawall, on the end of the penninsula, there is a camp store that sells just about everything a camper/hiker would need, including fresh steamed lobster. They even rent showers by the minutes. You're not far from Bar Harbor. Make reservations at the campground before you go.
If you have the time, take the ferry over to Nova Scotia (all night trip) then ride back. I haven't done this but a friend of mine did, he said it was a wonderful experience. It's on my to-do-soon list.