Well, the rumor mill says an xvid/dixv player is being created for the Zune by the freeware community. In the meantime,
New Zune hacks in town*- Use your Zune as a Hard Drive, Bypass DRM, etc, etc:
*You’ll need to make some simple registry adjustments in Windows, and the DRM bypass is…convoluted. Hopefully MS will just make an update allowing the player to be a backup device out of the box.