This may not be news to everyone; when I wrote some time ago that games were coming to Redbox, at least one commenter noted that the service was already available in his or her region. The company had previously launched a pilot program to test the viability of game rentals which, as you have no doubt surmised, did well enough to warrant a nationwide release. The currently selection offers some decent titles, with L.A. Noire (though as 1UP reports, L.A. Noire will be PS3-only, on account of the fact that the Xbox version spans three DVDs), Mortal Kombat, and Call of Duty: Black Ops among those listed, each of which will be available for a charge of $2/per day.
Aside from being a great way to try games about which one is uncertain -- say, if you're in the mood for an FPS with a hyper-masculine protagonist, whose name rhymes with "Nuke Dukem" -- one could easily play through a reasonably short game over the weekend for just a few dollars. LittleBigPlanet 2, also listed on Redbox's site, has virtually unlimited replay value due to user-created content, but for one who is new to the series, it's a helpful way to determine whether or not to pay the full retail price later. While it may a relatively expensive option - as a comparison, GameFly's Netflix-like mail service, allowing subscribers to keep one rental out at a time for $15.95/month (after the $7.95 introductory rate), averages just $0.50 per day - but for those who don't have the money for a monthly subscription, Redbox is a nice option to have.