Right now, through March 30th, you can get a FREE Redbox Rental Code (or promo code mail-in form, depending on state) when you text SMIRNOFF to 839863. (Standard text message rates apply)
I received a text back asking me to print off a form for 2 Free Redbox rentals. I'm out of ink though, so I clicked the "contact us" link at the bottom when you have problems printing. I fill out the form and they said, "Thank you for your inquiry. You will receive a printed copy of this offer via U.S. Mail within 5-7 business days."
(thanks Family Friendly Frugality!)
*Check the big list of Redbox codes here too for more free rentals!