You can try out the river for yourself.
The tweets come from my linkblog feed, which I create with Radio3.
In the video I say Radio UserLand was a linkblogging tool. It was that, but it was also a general purpose blog editor, and river of news aggregator. It came out in 2002. Radio2 was very much like Radio3, but it was server-based. Radio3 is written in JavaScript, and while there's a server component running in Node.js, most of the code is in the browser, as it is with the reader (demo'd above).
The aggregator that generates the river, which is in an open format, is also a Node.js server application called River4. It's open source.
Also there's Fargo but let's not get into that now.
Download the demo as a .mov.
Lots of software coming together here to make this all work.