Everything is a Remix

Here is an excellent web video series called Everything is a Remix that explains the history of derivative works and copyright. It is an excellent series. Check it out!
Part 1:
 

Part 2:
 

Part 3:
 
Link to Episode 3 Soundtrack

Part 4:

Link to Episode 4 soundtrack

Along with these videos, an excellent bibliography of samples and references has been provided, if you're interested in the content that was shown. It's very impressive.