Swap paperbacks (including children's books) for free
A while back we suggested Zunafish as a good place for swapping used books, video games, CDs, and DVDs. Christa pointed out that, unlike Zunafish, which charges $1 per transaction, Paperbackswap.com is totally free (books only, though, not other types of media). I checked it out, and the selection is astounding. We've got a ton of books we're looking to unload -- I can't wait to give it a try.