Backyard FX has a cool vid on how to make a suitcase full of fake cash. As a warning, please remember that this is to be used for film, stageplays, or LARP games. It is to be used as a prop and nothing else. Don't be stupid and end up in prison.
In fact, I would add something to the fake money that states something like, "prop money - this is not real," somewhere on the prop. The templates with Indy Mogul's Eric's photo on the dollar bills helps too.