If you love camping, my husband swears by Hermit Island. He has wonderful memories and went there every summer for a week or two. Although I'm not a camper (just seems like too much work to me) my husband has been lobbying hard for years. My DD8 wants to try it, so who knows.
Anyway, we do go to Maine most summers, and visit various places from York to Ogunquit to Kennebunck to Freeport. This summer wer went to Damariscotta, Pemaquid, and Boothbay. We also stayed at Freeport and used it as a jumping off spot for many day trips, and went shopping at LL Bean at night. Some of the best days we've spent were at Popham beach which is a state park, I believe. It never seems to get crowded. Huge expanse of a beach, rocks to climb on to get a great view. When the tide is out it makes great tidal pools and so forth, and when the tide comes in it really is quite a sight to as it fills in around the rocky outcropping. Some of God's best work!