Right now, Red Box has a Free 1-Night DVD Rental code to enjoy a movie night with the family. Use coupon code F2AMA8TG3 during online checkout.
I have never had an issue using these codes. You will still need to enter your Credit Card during check-out. You should not be charged unless the movie is late (return is required by 8p the day after your rental).
You can snag this freebie through 5/8/2013.