Within the past month, I have set up an account with Better World Books (BWB) for my library. They have this great program where libraries can send them their discards (age doesn't matter, but condition does - see the acceptance guidelines) at absolutely no cost except time. They pay the shipping, provide the boxes, it's incredibly easy!
And it's a great way to get rid of some of those deleted books. They do not take reference books, so we've had to find other homes for those (for those of you who may be curious, furniture stores will often take hardbacks - they use them to fill up the bookshelves that are for sale).
A few more details about what BWB does: they sell your unwanted books and recycle the ones they cannot sell. This is great for us, since book recycling does not seem to be available in our area. If your books are not "picked over" (put out for sale to patrons or offered up to other libraries), 5% of the profit made by BWB goes to a charity of your choice (well, they give you a list and you pick which one) and 15% comes back to your library on a quarterly basis! However, in our case, our books are picked over, so BWB makes all the money.
I first talked with the BWB guys at the ACRL Conference in Baltimore where they swiped my card and commenced contacting me shortly thereafter. They are very friendly and helpful. I have asked about a million questions via phone and email, and they patiently answered them all.
I highly recommend partnering with BWB. It's great to have a better way to get rid of our discards.