In the next version of Ubuntu - namely Lucid Lynx, you will find a well integrated Music store in the same lines as Apple's iTunes for Mac and Windows users. With one major difference namely - Ubuntu One music store will be selling DRM free songs. Each song will use 256 kpbs (or higher) encoding which enhances the quality of the song.
The Ubuntu One music store has been developed as a plug-in and so the users will be able to use it with a variety of music players in Linux. But in Ubuntu Lucid Lynx and above, it will be tightly integrated with the default music player - Rhythmbox.
Prior to buying songs from the Ubuntu music store, you need to create an Ubuntu One cloud storage account which provides you with 2GB of free space. The songs you purchase through the music store will be automatically transferred to your cloud storage, synchronized to all of your computers, and added to Rhythmbox.
Once you purchase the songs through the Ubuntu One music store, you can burn it on to a CD any number of times, Play through any software on any computer, and sync with any mp3 music device - even an iPod.
iPod users can use the Rhythmbox plug-in libgpod for transferring the songs.
Ubuntu has teamed up with 7Digital for selling music to Ubuntu users in this way.
Check out this nice writeup from a Ubuntu One music store beta tester , where he gives his first hand experience of this new offering from Canonical.
Source(s): Ubuntu Wiki FAQ, Ubuntu One blog.