You should try to do the duck tour. My mum and I did that and it was great - takes you all around Boston and you even go in the river to check out the waterfront. Lots of information and it's just an all around informative, quick tour. It leaves from the Museum of Science.

Also - go to the North End if you dig Italian food/stuff. They have awesome Italian restaurants and the most AMAZING pastry shops. North End is also where you can find the Paul Revere stuff (his home and the church he used to frequent).

Have fun! I had a great time when I was there