Every now and then theres a free app from Music Tao on the market that you can get free music downloads from. Problem is, they keep getting booted from the market. So far I think they've had 3 apps that I know of, Music Junk, iMusic, and Music Tao.
They may or may not make a comeback. If they do the app will probably have a difrent name and the developer might too.
Other than that, there's always Pandora, Last.fm, Slacker, and iheartradio for internet radio. All free.
Our Google, who art in Mountain View, Open Source be thy name, your Custom ROM come, your flash be done, on Phandroid as it is in XDA. Give us this day our daily Gingerbread, and forgive us our Rooting, as we have forgiven our Boot Loaders. And lead us not into iOS, but deliver us from iTunes.