Short bio: Computer Scientist, FOSS supporter (read more)
Tux Machines (TM)-specific
Although Boxee seemed the more obvious choice, it loses the high ground if you lack a decent internet connection. Just when I was about to give up hope, I heard about Enna – an incredible open source Linux media center, developed by the GeeXboX team, and ready for its first public release.
Enna can be installed on top of your Linux distro (e.g. Ubuntu) as a standalone app. But if you don’t want to make “the switch”, you can just use the GeeXboX live CD. You can boot Enna straight from the disk, without installing any alternative operating systems. If you want, you can even keep your default Windows installation running underneath.
Movies and Music
Keep in mind that the Enna Linux media center is a very standard app. It packs the very basic features in a most enticing and graphical user interface. If you’re looking for a surplus of widgets and online connectivity, you’re probably looking for Boxee.
That said, if you’re a standard media freak, Enna should sate your initial hunger, especially for a first public release.