To start with, if you are like me and know almost next to nothing about the Zune, then you might want to start with Zune@wikipedia. Very informative and covers what I think are the basics with articles that allow you to compare the different media players and the online music stores.
Zune.net - The official Microsoft Zune Site.
Zune Insider Blog - Very good zune resource. Kind of an mp3 blog for Zune users.
Zune User Group - Lots and lots of great info here.
Notes from YouTube - CNETTV have posted a first look into the new Zune 80. The video covers the differences from the first Zune and shows some of the new features that will be in the Zune 80. Including Wi-Fi syncing, audio and video podcasts, screen quality improvements, touchpad and the new operating system.