Just to keep the options going, here is another interesting service for getting digital audio resources for your school.
Simply Audiobooks has the option to rent, buy, download, and listen! What I particularly liked is the option to collect yourself a FREE download each month.
I grabbed free download of The Art of War, just to test the quality of this service out. I found quite a few relevant resources, though pricing is always a big question.
Managing the copyright labyrinth seems easy with this supplier.
Another interesting article is Downloading Books with iPods, from TechLearning.