I really liked this article. I've been playing around with some social-news-rating algorithms of my own, which are quite different from any of the ones listed here. One of these days I'll find the time to sit down and code a site around it them...

Also...I'm pretty sure that his argument for the "Dampening The Weighted Votes By Record Age" section is wrong. If you assume that each vote has the same weight (like HN, Digg, etc.), then you can rearrange the terms so that it's possible to use an algorithm that updates the 'rating' of the story on-the-fly.