I just signed up for and upgraded my Grooveshark account. It does pretty much everything that I was looking for Spotify to do, only cheaper.
As a general overview, this is a music player similar to LaLa in that you can listen to a radio station of magically picked music or you can upload your own music and listen that way.
Upgrading your account gives you access to the mobile application for Android, iPhone (soon), Blackberry, and Palm pre (soon).
The Android application allows you to take playlists that you made OFFLINE. That was the selling feature for me.
I’ll probably have more to say about this later.