(There are some known problems with this. ITunes will play Ogg once you’ve installed the Xiph Ogg QuickTime Component.
Ogg can be played on your Mac using Ogg player software such as iTunes or mirethMusic. The Ogg libraries are available on all computer platforms as open source. Because of this, it is widely expected that OGG will be quickly adopted by product developers and challenge the dominant positions enjoyed by MP3 and WMA. Although OGG is relatively new, it is also royalty free. OGG was developed by the open source community (the folks that brought us BSD and Linux) in response to the license fees being charged for using the MP3 format. OGG, short for Ogg, is a fully open, non-proprietary, general-purpose format for storing compressed digital audio.