Amazon wants a piece of the Android app development pie. Their app store is free in regards to submitting apps and there is less competition than in Google's Android Market. Apparently, they are also willing to part with a piece of their money to convince you, if you haven't seen enough reasons yet, according to TechCrunch.
Amazon has announced that beginning this morning any developer who submits an app will get a free 50 dollar credit to check out Amazon Web Services. This just does not include one of the services, it includes all of them, including some you may not have heard of. Amazon Web Services includes S3 (Amazon's storage service), Mechanical Turk (crowd sourcing tool), and DevPay (a online billing tool). 50 dollars may not get you far, but it will allow you to check out the services and use them while your app is being submitted and tested. It may even get you through the early days of an app's launch. After that, if your app is doing well, you could pay for renewal of Amazon Web Services.
However, this deal will not last forever. In fact, the deal is in effect until October 15th. After that, you're on your own. Just remember what you're getting into if one of your applications ends up being the Free App of the Day.