This is not official, but supposedly Google will launch its Google Music service today at Google I/O, and with some features that trump Amazon's Cloud Music, and some that don't. One of the best features that was "leaked" is that Google Music will be able to upload, store and stream 20,000 of your own songs for free, as opposed to Amazon's service handling only 1,200 songs. The one thing that Google's Music Service won't have that Amazon's does, is the ability to sell songs directly to customers. The service is expected to be rolled out to users within weeks of the announcement later today at Google I/O.
Source: Android.net via Engadget