One of our favorite Maine campgrounds is
Lobster Buoy Campsites in South Thomaston. It's really an old-fashioned, small campground with some delightful waterfront sites. And it's only a short walk to Waterman's Lobster Pound for the absolutely bestest lobster roll you will ever find.
There are plenty of lighthouses all along the coast -
here are some pix.
Here are some pictorial reviews and comments of some other Maine CG's:
Camden Hills SPLamoine SPWinslow Park in Freeport.
Overnight parking is allowed in Freeport in the LL Bean/municipal parking lots on the east side of Main Street.
Seawall CG in Acadia NP.
Have a great trip and enjoy the lobstah!
Ted H.