I've had a zune for about a year now. I've looked around a bit and have never seen anyone sucessfully able to hack one. I believe the proccessing power is either the same or more than that of the iPod so it is capable of running an OS similar to Rockbox. Since you guys seem to be able to hack anything that runs, I thought I'd post my question here.
Check out the Wiki on the Zune 30: http://en.wikipedia.org/wiki/Zune_30