There is already an excellent peer to peer network available for copyright free music. Lots of goodstuff depending on your taste.
The trend is toward the .shn format. I'm sure you could build up quite a collection and share it on gnutella as well. You can learn about it at www.etree.org or www.furthurnet.net

I don't know if I'm anxious to be embroiled in a lawsuit and counter sue for false allegations, but it seems like it would be very gratifying to offer up titles that are legal but might be assumed to be illegal bt the RIAA. Just to mess with them.