I have a small town park about four blocks from my house. It is full of trees that are hundreds of years old, and all the leaves I could want, for free. Small town park, so they don't care if I'm there stuffing bags full.
Oh yeah, and they conveniently rake them up in huge piles about twice a week. If I get there before they dispose of them, I can take as many as I want. Lucky me.
-Troy