Maine is a great choice for stunning landscapes, mammal, or bird watching. See also my field herping page for Maine. I have now taken four trips to Maine with the last two trips including Baxter Park and "Downeast". I would highly recommend getting away from the population centers in South-Coastal Maine and into the more remote areas where the most stunning landscapes can be found and it is still possible to enjoy true wilderness areas. Acadia park has some great landscapes to admire and is well worth a visit, but also attracts a lot of people so I would recommend a quick stop but spending the majority of your time elsewhere. If you are a birder, ruffed and spruce grouse are not uncommon and I have found both without too much effort in Downeast Maine, Moosehorn NWF has nesting ledges for Osprey and Eagles along charlotte road, and a trip to Machias Seal Island is highly recommend where you can see the puffins at the closest possible distance. Quoddy Head, Baxter State Park, and in neighboring Canada Grand Mannan and Campobello islands provide stunning scenery that will make any person with a camera seem like a National Geographic photographer. I recall one day parking along a road in Grand Manan island and sitting at a picnic table overlooking the coast. It was the most incredible sight I have ever seen still to this day. The waters were so alive with activity. Dolphins jumping, gannets diving, even whales and seals could be seen at the edges of the activity. The high sea cliffs, the beautiful lighthouse, even the ride on the ship to the island doubles as a whale watching cruise and I saw many from the deck of the ship.
A few helpful notes: Grand Manan offers cliff side camping which is highly recommended. Once you're in the more remote parts of Maine, supplies may be harder to come by or require longer drives than in more urbanized areas, so it's best to bring things like binoculars and camping supplies with you, or to plan to stop at a store on the drive up. If camping in Baxter State park, you'll need a way to charge your batteries, so look into options in advance. Additionally, once you're checked into Baxter State Park it is not easy to leave and re-enter the park as you wish. Your entry card has to be removed and a new one created each time you enter or leave, so generally it is far easier to come in with enough supplies for the duration of your stay there. Your cell phone likely won't work there either, so make sure no one is expecting a call from you on it. Finally, book your camping site for Baxter in advance or you may have to accept a less than ideal camping spot. If near Lubec, stop by the picturesque fishing village of Cutler. Consider hiking the Bold Coast trail for natural beauty (bring water, it's around 10 miles but you can turn back at any time if you get tired, there are views all along the coastal trail, the inland trail is mostly forested).
A few helpful notes: Grand Manan offers cliff side camping which is highly recommended. Once you're in the more remote parts of Maine, supplies may be harder to come by or require longer drives than in more urbanized areas, so it's best to bring things like binoculars and camping supplies with you, or to plan to stop at a store on the drive up. If camping in Baxter State park, you'll need a way to charge your batteries, so look into options in advance. Additionally, once you're checked into Baxter State Park it is not easy to leave and re-enter the park as you wish. Your entry card has to be removed and a new one created each time you enter or leave, so generally it is far easier to come in with enough supplies for the duration of your stay there. Your cell phone likely won't work there either, so make sure no one is expecting a call from you on it. Finally, book your camping site for Baxter in advance or you may have to accept a less than ideal camping spot. If near Lubec, stop by the picturesque fishing village of Cutler. Consider hiking the Bold Coast trail for natural beauty (bring water, it's around 10 miles but you can turn back at any time if you get tired, there are views all along the coastal trail, the inland trail is mostly forested).