Its not much fun in terms of night life but is a great place to chill, relax and wander around- there's lots of beautiful places to visit and the restaurants are phenomenal (if a little pricy).
Quincy Market is worth checking out (makes St. Lawrence look like crap) as is MIT, and the aquarium. If you're into cheesy pop culture there's always Cheers. In terms of clubs and stuff, you're probably better off finding some bar and drinking until you're kicked out at 2 am.