How does it work? You get a bunch of really cool computer games made by independent developers for... however much you want to pay! With the latest additions, you get 11 games for a minimum price of $7.60. Not a bad deal! You can even choose how much goes to the developers and how much goes to select charity organizations.
I would suggest you act fast on this deal -- not sure if it was around for very long the last time they did this. But trust me, it's certainly worth it -- I'm already having tons of fun with Braid and Osmos, and World of Goo was a really excellent experience. All three are innovative action/puzzle games that are really great in short bursts when you want to take a break from work (or other games!).