Audion for the Mac plays ogg files but there are some issues with it. First the older 2.1 version didn't play any of the ogg files I gave it even though it should have played them. Version 3 will actually play ogg files but the filenames must end with the .ogg extension. If you forget to add the extension playing the file will cause a crash.

Apparently ogg files have description tags similar to ID3 tags for mp3s but you cannot edit the ogg tags, only view them in the playlist. This is with OS 9.1 and the crashing problem might just be limited to my computer.