Its here... get it while its hot

http://www.microsoft.com/downloads/details.aspx?FamilyId=DF4AF56A-58A7-474C-BFD0-7CF8ED3036A3

Read the official announcement

Watch Michael Klucher do a demo

Read the GamaSutra article about Zune Development

Read the zune developer FAQ

But most importantly BUY A ZUNE!!! (and help ZMan pay the mortgage!)