Peaks-Kenny State Park — An 832-acre state park on the shores of Sebec Lake (it can get crowded in the summer, since it has a beach). All told there are about six miles of trails in the park. My favorite is the .6-mile Cove Loop.
Law Farm Nature Trail — A 1.2-mile loop—gentle and easy—through diverse ecosystems. Unfortunately (or fortunately?), the nature part of the preserve had pulled ahead when I visited, and the path was overgrown in sections.