Dave Winer’s implementor’s guide to rssCloud.
Following the news that WordPress.com has turned on support for RSS Cloud, maxpagels.com has also been updated to include this capability, thanks to Joseph Scott’s plugin.
The WordPress blog explains what RSS Cloud support brings to the table:
Right now how most people interact with feeds is by checking that it updated every now and then, usually about once an hour. Can you imagine waiting an hour to get your emails? (The world would probably be more productive.) RSS Cloud is an extra element in your RSS feed that allows subscribers to say “Hey, let me know as soon as you’ve updated, kthx.”
You’ll need an RSS aggregator that supports RSS Cloud to take advantage of this new functionality. Dave Winer’s own River2 is the only one I know that already supports it, but I bet many will follow suit in the near future.