Amazon has long offered music and movies for download and/or streaming. And now they've stepped into the wild world of video game downloads.
Amazon Game Downloads, still technically in beta (though open to the public), currently offers 600 titles priced at $10 and less. For any title in the store, you can download the full version and play it for 30 minutes before deciding whether or not it's worth a purchase.
As of now, it's definitely intended to be a service for casual games, but obviously Amazon will expand their reach as the market dictates in the future.