In honor of Redbox renting their 1 billionth movie, they are giving you a free rental with a rental. All you have to do is rent a movie, then go here to enter the code found on your movie. It is that simple. You will see a code on the screen to use the next time you go rent a movie.
Here are some codes that seem to be working for a free rental as well. You can only use them once per debit/credit card.
DVDATWAG - Only at Walgreens