When I lived in Boston I loved walking up in New Hampshire. The area around Franconia Notch (like Owl's Head) and the Zealand Trail, Crawford Notch, and Hale Brook are all nice. Monadnock is a nice walk, but very crowded, especially at this time of year. I did a lot of winter walking around White RIver Junction. And for easier day hikes the Berkshires in western Massachusetts are also really nice. South of Boston, the Blue Hills are okay, though more developed than I like. When I didn't have a lot of time to get up north I often rode my bike out to Walden Pond and walked around the woods in Lincoln and Great Meadows.
For a lot of information go to the Appalachian Mountain Club (AMC) on Beacon Hill in Boston. They are great!