All you have to do is plug in your Digg username (or someone else's) and it will scour your past dugg stories to serve up suggestions for stories both popular and upcoming. The more you digg the better the results should be. Not only does it show stories, but it also groups together keywords related to the things you like.
That's about all it does for now, but it's a wonderful way to discover new stories, and quite a bit more engaging than browsing the mass of stories in the upcoming section. Many people, including myself, have been waiting for Digg to get around to creating a suggested reading service. Until that happens, this is about the closest thing you can get.