Redbox offers a coupon code good for a 1-night DVD rental for free when you text "HEB" to 727272. (The coupon can be used at Redbox.com or within the iOS or Android Redbox App; it's unclear if it will work at kiosks.) That's a savings of $2. Deal ends September 16.
Note that this same code also cuts the cost of Blu-ray rentals to 50 cents and game rentals to $1.50.