I no longer teach 5th grade and have lots of multiple copies of books to get rid of... I tried posting them one at a time, but PBS wouldn't allow that.  Is there another way to do it?

Not really.  The system only allows you to post one copy at a time, if they share the same ISBN.  You could offer them in the Bazaar as a class set and see if anyone bites.

You could also put it in your signature. I would probably offer a 2 for 1 deal though. Something like: Classroom set of "Julie of the Wolves", 20 copies for 10 credits. Please PM.

Then when someone PMs you, you can arrange for shipping, buddying credits, etc. Of course, that is only effective if you post in the forums so people can see your signature!

There is also a new "header" feature for your bookshelf where you could put the same thing and it could be seen by anyone looking at your shelf. (I don't remember how to get to the page to edit the header though..)

What are the books you have multiple copies of?  I know I'm always curious about historical fiction and non-fiction (history) books as I don't have any class sets of anything to use (and there is no textbook for my 6th grade classes, so that makes life interesting).