This is a temporary page, soon to be moved to a newly-redesigned, OnEnsemble.org
Ogg is an audio format like mp3. It enables compression of audio to make music files smaller. It is higher-quality audio than mp3 for a given file size, but that's not the main reason I like it more than mp3.
mp3 is not truly free (as in freedom). Although end-users can use and share mp3's freely, software and hardware developers who create the software and devices that use mp3 must pay a royalty to mp3's patent owners. For those of us in the Free Software community, this means we can consume mp3s freely but not create them.
Ogg was created to be truly free, for end users and developers. It sounds better, and encourages creation. By using ogg instead of mp3, you empower software and hardware creators to create freely without having to pay royalties. See vorbis.com/software/ for software on Windows and MacOS that supports the ogg format. See fsf.org for more info on the Free Software movement.