There are many excellent land trusts throughout the state of Maine. They all do an excellent job of maintaining trails, gaining easements and conserving land for the future use of everyone.
IHT maintains many trails on the islands of Deer Isle and Stonington. We are both especially fond if IHT as we grew up in the DI-S area. The Tennis preserve is one of my favorites in Deer Isle.
Concentrated around Frenchman Bay between Steuben and Ellsworth there are several excellent trail systems. Most recently they have added a connector trail from their Baker Hill Preserve up to Schoodic Mountain in the Donnell Public Reserve Land.
There are many preserves that are part of BHHT on the Blue Hill peninsula. This is a very active group that is still expanding and adding trails. The most well known trail is just a half mile from their office and climbs up Blue Hill Mountain, the best place for a view of Blue Hill Bay and beyond to Mount Desert Island.
This land trust has a lot to offer along the midcoast of Maine between Camden and Belfast, an area we love to visit. The Ragged and Bald Mountain preserves provide excellent views just north of Camden State Park
Maine Coast Heritage Trust also keeps a list of Maine land trusts here