For anyone interested: The latest post in a series I've been writing deals (in part) with setting up a PubSubHubbub publisher, and how simple it is: http://blog.notdot.net/2009/10/Blogging-on-App-Engine-part-8-PubSubHubbub
-- Nick Johnson, Developer Programs Engineer, App Engine Google Ireland Ltd. :: Registered in Dublin, Ireland, Registration Number: 368047
