An unofficial version of GeeXboX has been released by Wiibrew developer Tulkas. GeeXboX is a port of the popular media player program for the Wii, and can play all audio and video files that MPlayer can.
This new version adds support for even more file system types. Though just what exact types were not mentioned. Tulkas also claims that he may have accidentally fixed a loading bug. Oh if only all accidents were so serendipitous.