This article on eMusic is quite an interesting read… If you have ever wondered if many companies sell music online that you can play on all your mp3 players (no DRM/windows media/AAC rubbish) then check out the article.
It has some glaring ommisions of course, most notably audiolunchbox who have the first 3 offspring albums among other mainstream music. Audolunchbox also sell only high quality unrestricted mp3’s so you can do what you want with your music. The big difference is that eMusic is a subscription model whereas audioluncbox is a purchase per track/album model. As it is all mp3 without DRM you can keep it all no matter what, but I am not sure if you are allowed to keep eMusic’s songs after you cancel the subscription – you’d have to check the details on their site (not that they can stop you anyway)