Some of the samplers are record label-specific, while others concentrate on a single genre or country, but for a limited time, they're all free. To see the selection, just click here or on the banner at the bottom of this post.
Of course, the good folks at Amazon.com are not without ulterior motives for their generosity. In this case, they'd like you to entice you into purchasing one or more of the "100 Greatest World Music Albums" of all time, which they've collected for your perusal here. However, while they've got some good stuff on their list - the Fela Kuti disc with Ginger Baker seems particularly interesting - there's no obligation to purchase anything to take advantage of the free downloads.