I love Maine, it is quite a contrast from Florida and for all the right reasons -and seasons-, first the excellent seafood is available almost anywhere you go, second the nature scene is colorful, rugged and inspiring, and while you wouldn't just head to the beach to catch some sun, you can go out for a hike through the coastline and have as much of a good time. The forest and coastline blend seamlessly and each season has something different to offer. Fall brings out great colors in the foliage and it is still manageable to be outside, but be aware some businesses start shutting down just before halloween, but since it is the end of season crowds are less prevalent. Spring and Summer is the best time to visit but it can be crowded, however the towns come alive and everything is in full swing.
Portland > Boothbay Harbor > Acadia National Park > Ogunquit
Portland is a charming city even though it has a town feel, the downtown area by the water is where everything happens, there are plenty of great venues, coffee houses, restaurants, etc. Here are my favorite places to eat in town: Dimillo's on the water, Portland Lobster company, Miyake, Becky's diner, Js Oyster, Eventide Oyster Co. While in Portland, check out Portland Head Lighthouse, Cape Elizabeth and Old Orchard Beach to the south.
Boothbay Harbor is quite the picturesque town and only an hour and change from Portland, the town of Wiscasset is on the way there, though much smaller and less touristy if you want to stop by for a bite to eat, I recommend; Red's Eats, Sprague's lobster and Sarah's Cafe & schooners pub. Once in Boothbay harbor, you can park and almost walk anywhere as the harbor is full of shops, restaurants and bars you can enjoy, and it also serves as a central spot to get to other destinations a few miles away, including: Pemaquid Lighthouse, Owls head, Popham beach. My favorites spots in Boothbay Harbor for some grub are: Mine Oyster, Fisherma's wharf Inn & Restaurant, The Lobster Dock, and Five Islands Lobster (though five islands area is located south of Woolwich, just before Wiscasset).
Acadia National Park is located 2.5 hours northeast from Boothbay Harbor, and there are a few stops to consider, like Damariscotta to check the Pumpkin Festival (Mid October), Marshall Point Lighthouse for some sightseeing, Candem for a coffee or a hike in Candem Hills State Park. The National Park has a few spots to check out, including: Bass Harbor headlight, Thunder Hole, Park loop road, driving up to the top of Cadillac Mountain and check out the panoramic views. Nested in the east side of the island is Bar Harbor, an eclectic small town full of character, make sure you spend some time there.
Only 45 minutes from Portland is Ogunquit, perhaps my top spot in Maine, this small town is full of life and energy, even in fall/winter time, you can walk from the center to town to the Ogunquit beach and back in no time. My favorite places to eat are: The Front Porch Piano Bar, Bread and Roses Bakery, Cornerstone Pizza & Craft Beer, Amore Breakfast. Do not miss Perkins Cove, a fishermen hotspot boasting a few great places to eat fresh seafood right off the boat, you can also head south to Cape Neddick and see the Nubble Lighthouse. Just a short drive north you will find Kennebunkport, another electric beach town, stop at the Rachel Carson National Wildlife Refuge for a short hike.