Update: And ... they're sold out!
There may be no such thing as free money, but in this age of digital economies we're getting quite accustomed to discounted fake money. Enter Walmart, which is currently selling 1600 MS Point cards -- that's $20 worth -- for $14.96. Thrifty Nerd tells us that you don't even have to pay shipping costs if you choose the in-store pick up option.
The Xbox Live Arcade House Party begins next month, including the likes of Torchlight and Beyond Good and Evil, so you might want to stock up on a few of these before they sell out. And they will, very fast.