scripting.com

A nice boost for rssCloud
  It's been a while since we could announce new major support for rssCloud, but today is one of those big days we'll remember for a long time.
  Status.net has now enabled rssCloud support in the RSS 2.0 feeds for all its users.
  This means that identi.ca, the server operated by status.net, has the feature, as well as all other sites they operate. I assume it will be baked into a subsequent open source release (status.net is GPL software).
  What does this mean? Well, when I post an update to my account on identi.ca, any cloud-aware aggregator will receive an update notification. River2, the aggregator I've built for Frontier (it runs in the OPML Editor) has support for rssCloud.
  For a demo here's a screen shot of an update I posted to identi.ca. Note the time of the update. I immediately refreshed the home page of my River2 server, and there's the update. Elapsed time ==> 12 seconds. That's what real time means. ";->"
  This is my feed. A source screen shot shows the <cloud> element.
  It's also a holy grail for the idea of a distributed loosely-coupled network of Twitter-like services, linked together in real time using RSS. (What a mouthful!) It's very elegant and lightweight and it works today.