First a few preambles... 
1. I'm a big believer in the River of News style of feed reader. Reverse-chronologic. Scan all the feeds every hour or every ten minutes, and accept notifications that feeds have updated in realtime. When there are new items, rebuild the river. 
2. For the last month I've been posting pointers to my personal river, so people can get an idea of how it works for a real person. 
3. A few weeks ago I issued a design challenge asking designers to take a look at the River of News idea and see if they could come up with a better way to display it. I'm using tables. They suck. Make it nicer. There was some interest, but so far nothing to actually look at. 
4. JSON may make the difference. It's the way you shoot data into a JavaScript app running in a browser. Or to a server-side app in JavaScript, or some other language -- they've all got JSON support nowadays. 
So... here's what's new: Now... 
When I build the HTML version of my River, I also build a JSON river. 
http://daveriver.scripting.com/index.json 
If you view the content of that file you'll see it's a series of updatedFeed elements, each of which contains a list of items that are new. 
This is the raw data of my River, with none of the formatting. In a language that every browser understands at its core. 
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Now it should be simple to experiment with new renderings. And not in a mockup. This is a real river, for a real user, that updates at least six times an hour, and usually quite a bit more often. (There are a number of frequently-updating realtime feeds I'm subscribed to.) 
One more thing... 
I released this last night as a feature of River2, an app that runs in the OPML Editor. To get the rendering for your river, you just have to turn on the Dropbox preference that allows a static rendering of the river. I will eventually add a dynamic page to the site that makes this step unnecessary. 
That's it -- that's the news. I'm pretty jazzed about this and hope to create some new connections.
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PS: It isn't just new in that this is in JSON, it's the first time there's been a data-only rendering of a river. 
Caveat: That I'm aware of. 
Update: There is now a JSONP version of the river. 