On the morning of your first day, visit the Farnsworth Museum in Rockland with its wonderful collection of paintings by the Wyeth family. Then drive up to Camden, one of the most charming towns along the coast, and take a two-hour excursion on a windjammer high-masted sailing ship. Consider staying at the Lord Camden Inn, in the heart of the downtown, or at one of the many delightful B&Bs.
On Day 2, drive up to Belfast, where you can wander around the downtown area, walk down to the harbor, and have a seafood lunch at the Weathervane restaurant at the harbor. In the afternoon, drive north on U.S. 1 to Searsport to browse its antiques shops and flea markets. Plan on spending the night at a B&B, such as the Captain A. V. Nickels Inn, on U.S. 1. A good choice for dinner would be Anglers, a favorite of the locals.
On Day 3, continue north on U.S. 1 to Bucksport to explore historic Fort Knox and go from there to the highest bridge observatory tower in America, atop the Penobscot Narrows Bridge. Spend the night in Bucksport, and have dinner at McLeod's restaurant.
Begin your itinerary in Rockland. Start with a morning visit to the Farnsworth Museum. Then head to Rockland's Maine State Ferry Terminal. Take the ferry (with your car) to Vinalhaven Island and spend the day exploring and watching the lobster boats and fishermen down by the harbor. Stay overnight at the Tidewater Motel (make advance reservations).
On Day 2 take the ferry back to Rockland and drive north to Camden, where you can explore the shops and galleries, try the excellent restaurants, and stay the night in a charming B&B. Spend your third day and night aboard a windjammer (arrange this ahead of time).
On your fourth day, drive to Belfast, where you can walk down the colorful main street, shop, and explore the harbor. For an authentic Maine dinner, take U.S. 1 across the bridge on the way to Searsport and turn right on Mitchell Avenue to reach Young's Lobster Pound. Stay overnight at the Belfast Harbor Inn nearby. On your last day, drive to Searsport and spend the morning exploring the Penobscot Marine Museum with its wonderful exhibits on the history of Penobscot Bay.