There are a number of current libraries that allow you to quickly and easily build out the subscriber or publishers pieces of the PubSubHubbub workflow.
These subscriber clients will allow you to subscribe a site or service, via the hub, to a feed from the publisher:
For more information on the subscribers and alternative frameworks and CMS systems, visit http://code.google.com/p/pubsubhubbub/wiki/SubscriberClients.
There are also a number of publisher clients available for use. These will allow you to implement feeds on a site that subscribers will be able to subscribe to via a hub. They will work to notify the hub of new updates from the publisher.
For more information on the ...