I have SwagGrabber on my RSS feed. She posts a lot of deals and freebies, some on the internet and others in physical stores. She's been posting about free Redbox rentals for awhile now but Jeff and I had never tried it.
Today we rented City of Ember. The promo code worked and the movie was free. Unfortunately, the movie was disappointing. Based on the preview, I was expecting some grandiose statement about life and about conquering environmental concerns, external conflicts, etc. For a kids/family movie, it was decent. But as an adult looking for content, it fell short. Oh, well. At least we didn't waste any money on it.
If you have Redbox in your area and are interested in a free movie, check SwagGrabber's website. She posts a free rental code once a week.