G-Tunes Music Lite is very good. Also I would like to mention Grooveshark, I think its better then MOG and Spotify. Check it out, you can create playlists of songs your pick. Save playlists and listen on your tablet, phone or computer. Very cool almost better then downloading.
Maestro is a social music websites and allows us to listen to music online. Grooveshark and a lot of streaming music websites only allow us to stream music on the websites. There aren't any download button for us to download songs directly. You might use a streaming audio recorder to download songs, but it is only for personal enjoyment.