Let me just cite Silvia's mail to the vorbis-devel mailing list here:

Sorry for the heavy cross-posting, but this is important.

Zen Kavanaugh, who used to develop the Ogg DirectShow filters has crossed over to commercial life and is now working at Microsoft where he is not allowed to continue working on Open Source media technology. It’s congratulations to Zen – but the DirectShow filters are now searching for a new maintainer. If you develop in Windows and are able to compile, test and package the DirectShow filters that are available from http://www.illiminable.com/ogg/ please consider taking them on.

At this point in time, there is not much actual development required – just the occasional application of a patch, compilation, packaging and then publication.

This is really important, so if you can help you should really consider stepping forward.

Go for it!

Cheers, Silvia.