If you haven't been using this, give it a shot.
Spotify is basically an iTunes replacement for music. You log in with Facebook and then you instantly have access to nearly every song known to man. It streams all this music straight to you.
It finds all your iTunes playlists and local music too which is handy. When you subscribe to a playlist it keeps it up to date too, so if the playlist owner adds some songs, your playlist gets updated. I've found a bunch of playlists that look good like 'Rolling Stones Top 500 Songs', 90s mixes, dubstep mixes, best classical music and shit like that.
Syncing playlists to your phone has never been easier, just open the app on your iPhone/Android and tick 'Available Offline' on the playlist you want. It will download it over your WiFi and let you play the song without streaming it. Just to be safe you can turn on 'Offline Mode' and 'Dont Stream over 2G/3G' in Settings so you never get a surprise from your phone company due to excess data.
There's a queue function too, which is something iTunes has severely been lacking forever! I am so glad this exists and use it extensively.
On top of that they have 'apps' you can add, there's a Triple J has an app which is great as it has the 'Hitlist' which gets updates as they play new songs on the radio, as well as the Feature Album (and all previous ones) and all their Hottest 100s just a click away. There's a Rolling Stone app with music news, a The Legend Of app that focuses on a different legend every now and then like Bob Dylan or Hall & Oates and much more.
The social aspect is pretty spiffy too, you can share a song/album/playlist on facebook or just drag it onto a friend and it will pop up in their Inbox. You can right click > Copy URL and embed on these forums very easily which is useful too.
The catch: There's a subscription fee to remove ads and have all the features. It's ~$6 for standard or ~$11 for premium if you want it on your mobile. The good news is that you can activate a 30 day premium trial for free! Without it you'll get annoying audio and visual ads popping in every now and then and not be able to access all features.
Do you use it, like it? Will you subscribe after the trial runs out? Do you use it on your phone?