From the registration of the ZuneSleeve.com domain:

Registrant:
   Microsoft Corporation
   One Microsoft Way
   Redmond, Washington 98052
   United States

   Registered through: GoDaddy.com, Inc. (http://www.godaddy.com)
   Domain Name: ZUNESLEEVE.COM
      Created on: 15-Jul-06
      Expires on: 15-Jul-08
      Last Updated on: 18-Jun-07

   Administrative Contact:
      admin, domain  This email address is being protected from spam bots, you need Javascript enabled to view it
      Microsoft Corporation
      One Microsoft Way
      Redmond, Washington 98052
      United States
      14258828080

   Technical Contact:
      admin, domain  This email address is being protected from spam bots, you need Javascript enabled to view it
      Microsoft Corporation
      One Microsoft Way
      Redmond, Washington 98052
      United States
      14258828080

   Domain servers in listed order:
      NS1.MSFT.NET
      NS5.MSFT.NET
      NS2.MSFT.NET
      NS3.MSFT.NET
      NS4.MSFT.NET

As you can see this one has been registered a year ago, but till now we haven't seen any Zune jackets or clothes available to the public, although there are some clothes (t-shirts, jackets) created for promotional reasons e.g. for the Zune Masters project. Also the domain doesn't have an active website.

But ZuneSleeves.com registration info shows nothing about Microsoft, as it is registered using dreamhost's hidden registration service or something. In any case the ZuneSleeves moto is this: Zune sleeves: change the way you listen 

EDIT: OK I had an idea: to check the text strings in the Zune Logo. An innocent, plain Zune logo. But it has been created on Photoshop... for Macintosh. So stay clear, this one can be an iFanBoy site, you have been warned :

Adobe Photoshop CS3 (10.0x20061208 [20061208.beta.1251 2006/12/08:02:00:00 cutoff; m branch]) Macintosh

[via Engadget , IWAPZ ]