Updated with new codes. Below is an easy way to get free promo codes good for a free $3 off coupon on DVD rentals at all Blockbuster Express kiosks. Their rental price structure has changed to $1 to $3 a day depending on how new the movie is, so these are again free rentals.
New method: You must text a special keyword to 39777 and receive a unique one-time use promo code back via text message that will expire in 10 days. The code takes $1 off any rental transaction. Active keywords (newest listed first), usually found via Slickdeals:
Does not cover additional nights. Unfortunately, you can’t use Google Voice to text the codes. You’ll need a real cell phone or some other alternative (let me know if you find a free one). Make friends with someone with unlimited texting, possibly the person in front you in line in front of the kiosk.