pubsubhubbub - Project Hosting on Google Code

pubsubhubbub - Project Hosting on Google Code: "A simple, open, server-to-server web-hook-based pubsub (publish/subscribe) protocol as an extension to Atom (and RSS). Parties (servers) speaking the PubSubHubbub protocol can get near-instant notifications (via webhook callbacks) when a topic (feed URL) they're interested in is updated."