Redbox is a big red box (i.e. the name Redbox) where you can rent movies from for just $1! I usually see these in my town outside of Walgreens and Walmart. But, they are other places too. For example, in larger towns I see them at McDonald's. Go here and you can search and find one in an area near you.
You just use a touch screen, click on a new release of your choice, swipe your credit card, and your movie slides on out! Good know too is that you can return these at any Redbox, not just the one where you rented it from.
I rarely pay for movies from these machines because there are so many promo codes. One way to get free rentals is by signing up here. You will get promotional email alerts with free codes.
Here are some I have used:
REDBOX (New Customers Only)
WALGREENS (Walgreens Only)
You can use these once per card. But, you if you have a different credit card/debit card then you can use it more than once.