I am doing a free DV project for a local non-profit. Do I need any kind of contract with them? If so, what kind of items should be in it?

Yes you need a contract. Protect yourself all the time. I have found to my expense that "non-profit" only applies to volunteers, not management, and people that can run expensive offices through NPOs don't have any qualms about making things very bad for you, if they aren't satisfied, whether they paid or not. I no longer do any free work because it brings no respect only trouble.