Following on from my lst post about Pubcon, I was looking through my notes and I figured you may want to see a couple of sites that were noteworthy on the Social Bookmarking scene

Pligg - a content management system allowing you to have your own 'digg' type site. Being opensource, its free.
My commnent: you need a vibrant community to make this work well and you need to be at the hub of this community so you can get the votes for varoius submitted stories. A great example of this niche community site is Sphinn, a site geared to SEO, SEM

Buzzlogic - a 'hub identifier'. 
The big thing these days is targeting influencers who other sites reference from. I've covered this somewhat in my last post with http://www.blogpulse.com/