You've probably seen them outside the supermarket. You know - those big red vending machines. But instead of a soda for $1.25, you get a movie. For $1. Swipe your credit/debit card, and the disc is all yours for the night. That's Redbox, and the machines are popping up everywhere, ready to supply the masses with low-commitment, impulse-rental DVDs. With 20,000 machines, each holding about 500 discs, Redbox is making tons of money. And some Hollywood studios are going ballistic.