At a wargaming club with a large RPG group I literally could not give away my copy of the 4E Players handbook. I did try. None of the RPG group even knew of someone who was playing 4E and would find a good home for it. So I've decided to put in with the next lot of books I donate to the Charity shop and bookcross it for good measure - see where it turns up.
Last time I donated books to the charity shop I gave my copy of Dawkins' "The God Delusion" to Christian Aid. Tee Hee.