Mount Tom State Reservation – Holyoke and Easthampton – Great views, hawk watching, visitor center. 20 miles of walking and hiking trails.
The William Cullen Bryant Homestead – Cummington – Walking and hiking trails, birdwatching, picnic area, historic home and barn.
Arcadia Wildlife Sanctuary – Easthampton – 5 miles of walking trails near the Oxbow.
Chesterfield Gorge – West Chesterfield – Very nice walking and hiking along the Westfield River. 1/2 mile trail along the top of the gorge. Seven mile hike on the East Branch trail. Public restrooms and picnic area.
Mount Holyoke Range State Park – Amherst (Hadley to Belchertown) – over 30 miles of walking and hiking paths, including the Horse Caves and the Notch. The visitor’s center on route 116 in Amherst is open daily.
JA Skinner State Park – Hadley – 400 acres on Mount Holyoke, including the Summit House, visible from many parts of Northampton.
Mineral Hills Conservation Area – Northampton – short hikes along a ‘paper’ roads network. No major views, but a nice walk in the woods. I found the trail markings a bit confusing, though. The parking area is off Sylvester Road in Northampton.
Williamsburg Woodland Trails – Williamsburg – walking and hiking trails in and around Williamsburg.
The Massachusetts Department of Conservation and Recreation – provides a searchable listing of state parks with descriptions and maps
Trustees of Reservations – “Find Your Place” page provides a listing by property name as well as a clickable state map