If you haven't already heard Amazon has opened a DRM-free MP3 based music store. Good times, music that you own rather than rent
. Not to mention you can play it on anything that supports the MP3 format. Anywho, currently it seems that linux users can only download single songs rather than whole albums since they do not currently have a download utility for linux. Not to fear according to their docs
If you use Linux, you can currently buy individual songs. A Linux version of the Amazon MP3 Downloader is under development, and when released will allow entire album purchases.