If you submit articles to Digg, or plan to anyway, here's a good look at how they rate articles. Getting a good rating (diggs) can bring a lot of traffic, as well as build one way links...

http://www.marketingshift.com/2006/9/digg-algorithm-elements-confirmed.cfm

"Here is a condensed version of what Kevin Rose & Jay Adelson confirmed as being some of the core elements used in determining the ranking (could substitute relevance here) for a story on digg."