you can actually use doubletwist for free it is only 4.99 for the airsync feature
there is the amazon cloud drive as mentioned,
google music beta if you got an invite(kind of sucks lol i tried it for a few days i will check it again once they have a better layout)
or as jklitten said follow those steps and just copy the music to th e phone. All itunes music is now DRM free so you can continue to buy music there and just copy it to the phone.
You can also use dropbox to move the files over pending how big you music library is and how much space you have for dropbox this could take a while.