Copyright Explanations Done Right
I know that Cory Doctorow gets up some people's nostrils - there's even a site dedicated solely to his denigration - but you've got to allow that the man (a) knows what he's talking about when it comes to copyright and (b) can really write when he has a following wind.
I offer Exhibit A, entitled "How Copyright Broke", without doubt one of the most accessible introductions to where copyright came from and what's wrong with it. It's the perfect solution for explaining a tricky subject to aunts and uncles.