There is this great new application called Mobbler, that allows you to login to LastFM account on your mobile and to stream music. The set up is pretty basic and it worked very well provided there was signal.
I tried it out on the train this morning, and it was not as reliable as I had hoped. Once it loses connection, you have to manually reconnect. (Lets hope this gets changed in newer versions as it is a right pain if your phone is buried in your pocket).
Overall I like where they are going with this application and would highly recommend using it!
Note: you need to have an account on LastFM before trying to use this application. You can sign up here.
If you log into LastFM on the web, you’ll notice they have updated your library, which is very cool.