Can you Freecyle them? People who do wedding DVDs or college students who save information on CDs would probably get a lot of use out of them, as often it's cheaper to buy 100 DVDs/CDs without cases. My husband does a lot of video editing work and we actually paid about $20.00 for a bunch of new DVD cases that we bought off the internet. Otherwise, check with your local schools. As a teacher, I got so many freebies that came without cases, I'm sure other teachers could definitely use them.
Hopefully one of these ideas works!