I have a couple of music files in Ogg Vorbis format, a format that iTunes does not support by default.
Before, I used the Ogg Vorbis QuickTime 6.2 component written by Jordan Mendelson. Notice, however, the “6” in that title. Mac OS X 10.4 “Tiger” uses QuickTime 7. If you come to a Ogg Vorbis song file in your iTunes playlist on 10.4 when you have Jordan’s component installed, iTunes crashes.
No good! Luckily, Arek Korbik has written a new Ogg Vorbis QuickTime component that works with QuickTime 7.
Even cooler than that, the above page is really a bit of a developer Weblog, describing some of the steps he’s taken to make the component. If he got himself an RSS feed, I’d subscribe. He even has a teaser: “Watch this space.” Guess Apple isn’t the only one keeping secrets, eh?
Weaponized Fluff 
Hi. Thanks for the pointer.
But it still won’t play oggvorbis over daap from my linux box 😦
Any idea why is that? It seems to think that the files are some sort of mpegs, when I “get info” on a remote ogg vorbis it says “Kind: MPEG audio file (remote)” which is of course not true.
Short version: I have no clue.
There doesn’t appear to be any public DAAP information, despite the fact that this page
http://daap.sourceforge.net
says that such docs were sort of promised back in 2003.
It may be that you’re supposed to get such support “for free” by using the right APIs when making your plug-in.
Considering that the plug-in is Open Source, your best bet might be to compile and try it for yourself.