[kevman]

I'll second the Fenway park tour. Definitely worth it no matter how much you like baseball.

There is also a free walking tour of the historic sights put on by the parks service. I don't know where it starts but we just kind of stumbled into it and found it quite interesting.

If you're only there for a day you'll be more than entertained by simply wandering the streets. It's such a compact city that everything is within a short walk.

Harvard and MIT are also cool. Just because of what they are.

Do you have a hotel booked yet? We stayed at the Onyx right downtown. They have cruiser bikes you can borrow for free and welcomed us with complimentary ice cream sandwiches (the best ice cream sandwich I've ever had). When I forgot my shaving cream they just gave me one. There is even complementary wine for an hour every evening. Such a refreshing change from other hotels that nickel and dime everything.