Amarok and Magnatune
I haven't tried the Linux music player Amarok, but they just added Magnatune to it as a music store (I'm on Magnatune). Pretty cool:
Amarok continues to blast ahead with release 1.4.4. We're thrilled to be able to take our long association with Magnatune to new heights with the addition of an integrated DRM-free music store with full-length mp3 previews. Magnatune's "we are not evil" attitude guarantees that you can purchase awesome tunes and the artist receives half of the purchase price.
Also I should probably say I'm totally loving Ubuntu. I can't imagine using it on my main desktop, but it's been wonderful to me after some disasters at the hands of SuSE and plain ol' Debian. The default brown theme needs to go though.