Redbox on Facebook on or before Monday, June 21st and you'll get a personal code good for one free rental. The code will only be valid on the 21st until 8:59 PST, which is perfect for a Monday movie night! Just be sure to return your movie the next day before 9pm to avoid getting the $1 charge for your movie.
They're a little bogged down with code requests at the moment, but should get everything sorted out before the 21st so don't worry if you don't get your code right away. Thanks Redbox!