Amazon Cloud Player streams music from your free Cloud Drive to Android and the desktop
The Amazon Cloud Player allows you to stream music stored on your free Amazon Cloud Drive in either MP3 or AAC formats directly in your browser or through the use of the free Amazon MP3 Android app. The Cloud Drive will let you upload and store almost any type of content file you like, with 5GB of free storage available to everyone with an Amazon account. If you buy an MP3 album from Amazon, it'll bump your Cloud Drive storage to 20GB for one year for free, while any MP3s you buy from Amazon are automatically added to your Cloud Drive and won't count against your storage quota. If 20GB isn't enough space for you, or you don't want to buy your music from Amazon, then additional price plans ranging from 20GB to 1000GB are available for $1 per gigabyte per year for US-customers.
Use of the Cloud Player requires a valid US-based billing address at the moment, which is likely tied to licensing agreements with record labels, but anyone with an Amazon account can use the Cloud Drive to store files. It's also not available for iOS, not even in Mobile Safari, but according to TechCrunch it has nothing to do with the lack of Flash.
Head on over to Amazon's Cloud Drive and Player getting started page, to get yourself 5GB of free cloud storage, and if you're in the US, free music streaming.