Finally got the last codec I needed on my Mac Mini to be able to play back any video file I have found thus far, and figured others might have a use for this. My goal was to get Quicktime specifically to play these, as that also means they can be imported into any iMovie/iDVD project. This should have the ability to allow iTunes to play back these as well, along with Front Row on the new iMacs. If you don't have a huge need to edit or play back via Front Row, then using an alternative player like MPlayer or VLC works too.

Anyhow:
Divx 6: http://www.divx.com/divx/mac/download/
XVid delegate: http://people.ee.ethz.ch/~naegelic/download/
3vix: http://www.3ivx.com/download/macos.html
AC3/A52 decoder: http://sourceforge.net/project/showfiles.php?group_id=83360
WMV Decoder for Quicktime, commercial, $10: http://www.flip4mac.com/wmv.htm
Quicktime MPEG2 decoder, $20: http://www.apple.com/quicktime/mpeg2/

If someone comes across a video this can't play back, I'd be interested in getting a copy to then try and get it working.

That is really useful. Thanks dude!

Nice list. Thanks.

Have you had success with the WMV QuickTime codec? I tried it out and it didn't work well for me. I don't remember what the specific problem was, just that I didn't think it was good enough to be worth using. Maybe they've improved it?

The WMV codec is working for me on both a Mac Mini and Powerbook. While they studder with WMV-HD content, even my P4 3.2 does too, so no real difference there.

The trial is slower then the unlocked product by a noticible amount though. It seems due to the scrolling trial message it applies to playback, and also ensuring it cuts off at 50%.

I've only had experience with version 1.0.2 though, so maybe it is an improvement over older versions. Not sure.

FWIW, the playback WMV codec for Quicktime is now free from Microsoft.

That list can be simplified a lot as well now:

Perian - for nearly everything except WMV and MPEG 2. This includes divx, MKV, and some others.

Flip4Mac as noted, free now that MS dropped support for their own Windows Media Player on OS X

Quickime MPEG2 component, still $20.

Thanks. I wish I'd known about that before. Uninstalling the official DivX codec is a huge pain.

I was very grateful when you BBS folks helped walk me through getting rid of the official Divx codec that was making my QuickTime encodes crash. :-)