There are a couple - such as a new version of AIM - that are being given to and used by developers to test Apple's push notification servers. These include push notifications, but there aren't any that include them that are publicly available.
Right. Though many developers have demoed their push services both at WWDC and Macworld, nothing is available to the general public as of this time. The two that have gone through, and are going through the Apple developer betas are AP News and AIM, though i remember espn demoing their app a while back as well.