pubsubhubbub — I’m not kidding — is an actual existing thing. Yeah, I too would have killed to be a fly on the wall when they decided to call it that, but there you go. So let’s dissect this piece of art of a name:
pubsub, i.e. pub/sub, i.e. publish/subscribe, which is a common pattern in, well, the world, where multiple parties subscribe to one or more publishers, to receive notifications on updates.
hub, is a center of communication, often used for efficiency purposes, like an ethernet hub.
bub, you tell me. I haven’t a clue.
So what is it, really? It’s a protocol to enable near real-time update notifications among pubsubhubbub-supporting parties. Whereas RSS and Atom feeds required polling to receive updates, pubsubhubbub pushes information to parties. Currently various Google properties are have pubsubhubbub-support, such as Google Reader and Google Buzz. So, when you install a pubsubhubbub plug-in for a wordpress blog, like I have and I push the publish button on a post, it will almost instantaneously appear in all of your Google Readers and your Google Buzz, whereas before, it may have taken a few minutes or hours to appear.