During Fall of 2011, we stayed in Salisbury State Park, Massachusetts. I recommend it. It's just a large, open campground with river and beach frontage, but it was a nice place to stay. It may book up in the summer, so reserve as soon as you can. We were there in late September and they had plenty of room.
We stayed in Camden Hills State Park, Maine, and enjoyed it also. There were some wooded sites large enough for our 31 foot Sunseeker Class C. There was also an open area that was basically a meadow with room for any size RV.
We couldn't get into the Arcadia National Park campground so we stayed in the privately owned Bar Harbor Campground. It was nice. They had a big variety of campsites, including some overlooking the water and some that were secluded in the woods. It rained one afternoon so we used their nice laundromat. We found out that when the alcohol cooks out of wine in a crock pot stew the LP alarm will go off!