If you are an avid reader and your house is getting to small to house your read lit, book donation might be something for you. There are a lot of libraries and charities that love to receive your (unwanted) books.
The people from Bibloobuffet have put togother a great list with charities all over the world. There are some very special organisations there. What to think of the Camel Book Drive? You can find the list here. You can also find a list on this website. As said, libraries also like to receive books. Click here for a list of libraries that are in desperate need of books.