Hands Across the Water offers a free outlet to donate old books to:

Our Concerns–are they yours also?

Hand Across The Water delivers an effective solution to two problems: the domestic problem of excess books and the global problem of not enough books. We collect books from schools, libraries, and individuals who no longer want them, and send them to schools and libraries which desperately need them. We care about less affluent people who do not have enough books to sustain educational and intellectual growth and are condemned to ignorance, illiteracy and poverty. We are dedicated to cultural bridge-building on a local, national, international scale by providing the tools of literacy and education.

http://surplusbooksforcharity.org/whoweare.html

A noble cause, but hopefully the books they receive will be of high quality rather than old cookbooks or books so bad that nobody wants to read them.  Their blog does offer uplifting tales of where the books go and why they’re appreciated.

They do have a drop-off center in Allston, which is not too far away.  Think I’ll use them the next time I feel like cleaning out my bookshelf.