Hey marcus22, coming from Quebec City, route 201 is a nice ride into the state but it is known as Moose Alley so beware around dusk or after dark. I'm kind of partial to the western part of the state from Rangeley south zig-zagging into New Hampshire and back (another moose alley). The coast is full of quaint little towns with shopping, restaurants, and what not where you can visit many forts and lighthouses. Let us know when you visit, maybe we can meet for a coffee... There are others on here from Maine, I'm sure they'll chime in eventually...
If you get to southern Maine, try and stop in at Bentley's on Rt. 1 in Arundel. I also like the ride from Portland over 302 through Bridgeton to North Conway, NH.
Sorry, addressed the wrong person in my previous post but anyway marcduf, I wanted to add a couple of links for the forts and lighthouses, Check out Historic Forts of Maine and Maine Lighthouse Map . Also, route 17 between Rumford/Mexico and Rangeley has some nice western views. The road was just resurfaced last summer so should be in pretty good shape still. I know a lot of people like to ride the coast but it's just a little too busy for me, very nice though.