I just became aware of this project Creative Commons that is an effort to create a new type Copyright symbol, (CC). By putting (CC) on your work it means that you are explicitly telling others that it is OK to create certain types of derivative works of your original. Under current Copyright law, a work is assumed to be copyrighted whether you say so or not. This has created nightmares for Djs, musicians, artists, authors, etc. who want permission to include snippets or derivative works of other's work in their own-- Basically you need a lawyer to figure it out. (CC) sounds like a great idea. I think I'll make all of my music (CC).
There's a great flash animation here that explains everything.