Introducing Amazon Cloud Drive, Amazon Cloud Player for Web, and Amazon Cloud Player for Android
Buy anywhere, play anywhere and keep all your music in one place
Start with 5 GB of free Cloud Drive storage - upgrade to 20 GB free with purchase of any MP3 album
Is mainly for MP3 so you can buy them online and access then from anywhere but you can store anything on there, photos, documents etc.
The music player works with Android apparently as well as PC but not tried it yet.
Purely as online storage, this is potentially way better than drop box IMHO just for the 5GB rather than 2GB.
20gb free is available to "Only residents of the United States with a United States billing address are eligible for this offer."