There is a little hole-in-the-wall place in Howland, Maine called Jim & Jill's. Jim is the cook and Jill is the waitress. They are the only two employees there and this little restaurant is their baby.
Jill is extremely friendly and Jim is a fantastic cook. The prices are absolutely realistic. The portions are a little bit larger than what you'd serve yourself at home, so you MIGHT have leftovers if you opt for desert, like some of Jill's homemade pie.
They have a full bar and several beers on tap and bottled.
The place is just off from exit 217 on I-95, or about 2 miles from Rte 2. The drive north/east along Rte 2 is absolutely fantastic in the summer with the top and doors off the Jeep. It runs along the Penobscot River and offers a nice wide road with a decent surface for bikes. The only drawback is you may encounter logging trucks running between Lincon and Old Town. (about a 25 mile stretch)
Another great place with fantastic seafood is on Rte 178 in Bradley.
Claudia's Seafood, just a few miles off from Rte 9, on Rte 178 is a 15 minute ride from Brewer (Bangor's sister city). They have a large screen-house for folks who want to eat there, they ship lobster and other seafood anywhere in the country.
My girlfriend and I have been known to be out for a ride in the Jeeps and called ahead to have a couple lb of steamers ready for us when we arrive. It's actually located across the road from a Jeeping-trail access road. It's not uncommon for us to go out jeeping and give them a call as we near the end of the trail. Stuff our bellies with some tasty ocean treats, then head home to Bangor for the evening.