Maybe not the greatest solution as it costs money but there is a service called mp3Tunes (
http://mp3tunes.com/) that allows you to upload your mp3s to server that they host and then you can stream them back to yourself using select radio. I used the free trial and it was pretty cool. I havent paid for the service but its a neat idea and your mp3s are backed up remotely. I have 233 Gigs of MP3s though so I have no hope of fitting them all on anything.