At studenthacks.org we just found 10 creative ways to reuse old books.
We've been using Bookmooch to trade books for the past 3 months (a detailed review of that service is coming soon), but there are some books that no one seems to want to borrow. We can't give them away, and we know we'll never read them again. So why not turn one into a bookshelf, or a clock? Or, like the pictiure above, an iPod case.