Spent a few days there last year. It is a beautiful city with plenty to see and do.
The freedom trail is a walkway through the old part of the city which guides you through all the major sights. Most of the sights have guides in period costume explaining the history of the area. The state house is worth a view, it's like the highest court in the state of Massachusets. Beacon hill area is great for walking around, very "olde worlde", it still has gas lamps on the streets.
Then, of course, theres Cheers bar. Well, two of them actually. The original one is a wee pokey hole and quite grubby inside so they made a bigger one in the city centre.
Lots of excellent beers to try
Well worth a visit.