I found this great idea on how to use the ones I will never read again at Redefine Creativity... by making holiday ornaments. Alisa Burke has some other great ideas for upcycling your old books too.
Supplies needed: styrofoam ball, old book pages, glue (I started with stick glue, but switched to permanent fabric glue halfway through - it seems to hold better), hot glue gun, ribbon.
Set aside to dry. Once completely dry, attach the ribbon to the styrofoam ball - forming a loop to hang your ornament with.
I love this idea so much!