Another day, another social music tool.
Anywhere FM allows you to upload your own iTunes library online - so you can listen to your own music library anywhere via a broadband connection. It also has a very slick iTunes-esque interface. And the novel social music twist is that you can listen to other people's music libraries - or rather, you can stream their playlists as a personal radio station. Like last.fm, you get a "compatibility" rating to see how you compare with your fellow Anywhere FM listener's tastes.
As others have pointed out, it enters a crowded market, competing with the likes of MP3 Locker - but it is free. And the social music angle is quite interesting.
It is early days for the service - though as of this evening, there have been 350,000 songs uploaded. And the music selections it provides are good.
Would be good if they added the ability to scroble to last.fm though.