What an excellent idea one homeschooling mom had; a free exchange list
on Yahoo Groups. It seems to operate a lot like Freecycle if you've
ever heard of it. If you have extra, unused, or no longer needed
homeschooling materials, you post an 'offer' message on this list for
other homeschoolers to see, and if someone needs it, they email you
directly. After the exchange has been decided, the the 'giver' posts
that the item has been taken. It can also work the other way; if you
need a certain item, you can post a 'needed' message and if someone has
it to give away, they email you directly, and the 'needed' person posts
that the request has been fulfilled. This is a relatively new group,
but I can see it going far! Good luck to them!

http://www.groups.yahoo.com/group/freehomeschool