XMPP service - Google App Engine

With the introduction of the XMPP service to App Engine, it's now possible to write an App Engine app that communicates with users - or even other applications - over XMPP, otherwise known as Jabber or Google Talk. In this article, we're going to walk through an example that covers all the basic functionality of the XMPP API.
http://code.google.com/appengine/articles/using_xmpp.html