I'm a big fan of Mount Sunappe. For me, it's the best "real" mountain close to Boston. Pat's Peak is great for kids but pretty limited and Crotched is bland and boring except for the park. I haven't been to Wachusett but I hear it's crowded anytime there's enough snow to make it interesting. Sunapee is big enough to offer a variety of trails, has consistent snow, but doesn't get too crowded. It's probably not much for nightlife, but being only an-hour-and-45 from Boston, it's my favorite for a quick blast north.