There doesn't seem to be any apps supporting it at the moment, the app store link leads to a dead end. Think we'll just have to wait for apps to be updated with passbook support.
1. Bend over and grab your ankles
2. Wait on Apple to allow publishing apps compiled using iOS6 SDK
3. Wait on Starbucks to submit app
4. Wait on Apple to review and approve app
5. Update/Install
6. Go buy yourself some $6 latte.
see Menel's funny post. People need to understand Passbook won't work until developers develop for it. Until then, make fake passes and play with those. Or develop your own.