PHP Pubsubhubbub server
I'm looking for a standalone Pubsubhubbub server written in PHP that I can use to test pubsubhubbub implementations locally without internet access.
It seems that Zend Framework has some server code, but that's only a lib and no server that can be used out of the box.
Since 2015-04-01 I'm using my own, self-written and self-hosted PubSubHubbub server called "phubb".
To help keep things simple and limit potential abuse ...[it] will only allow subscriptions ..[of] of the WordPress blog that it is installed on.
Installing Wordpress locally is done in 5 minutes, and using the plugin shouldn't be that hard.
Edit: Yes, that one is on the official hub list and I originally dismissed it since it's not a standalone server, but hey, there doesn't seem to be more.
As of 2011-07, there is a drupal module implementing a PuSH hub.
At the moment there only seems to be one implementation of the Pubsubhubhub protocol. That's the Google App Engine implementation.
Here's a slideshow going through the construction process of it if you're interested in creating another implementation: http://code.google.com/p/pubsubhubbub/wiki/BuildingAHub
StatusNet (http://status.net/) also implements a hub internally, but it's not available for other applications.
Another option is to use http://superfeedr.com/. We host most of the hubs out there. It's often easier to use existing solutions than re-invent the wheel :)