It’s the Digg era, with popularity driving content on all sorts of sites. What I haven’t seen yet (of course, maybe you have) is a site that lets popularity make the evolve. Start with  50 categories of stuff. News, sports, humor, video, celebrity gossip, blogs, etc. Put whatever you like at the top, however many items in each list. Doesn’t matter. Because an imaginary algorithm readjusts everything as stuff starts getting hits. Popular categories would get longer and move up on the page. Unpopular stuff would shrink, drop and even disappear. Visitors, of course, could suggest new categories, and even map links to them. But those too would grow or disappear with the Darwinian algorithms. Hard to imagine what you might end up with.