You can get a free Bing shirt for your Xbox avatar. To get this offer

1. go to bing (You’ll need to sign into the US version of Bing to see the gift.)

2. search xbox avatar bing shirt (or you can use this link)

3.  get the promotional codes

4. Read http://support.microsoft.com/kb/908637 to know how to redeem them

[Via Major Nelson]