As a college student in Boston, I am ALWAYS looking for free and cheap things to do in the area! I found this article on the Boston Globe website that anyone thinking about visiting Boston should look at: http://www.boston.com/thingstodo/gallery/free_events/

I've done several of these: the ICA, the MFA (although as a college student it's always free for me), shows at the Hatchshell, Shakespeare on the Common, the Peabody Essex Museum. Except for the cost of getting to the location (and I chose to walk to most of them), it was free!