AbstractPlus view in PubMed
Flags and Lollipops discusses a Greasemonkey script that adds TrackBack links within PubMed, designed to work with the AbstractPlus view.
I really like the AbstractPlus view (sample citation here) -- in a recent search that included mostly case reports, I found some useful citations that otherwise would have likely taken much more "looking" to find. It also has helped me make some connections with related concepts in the literature. (More on PubMed's Related Articles algorithm and the AbstractPlus view)
Also, if you haven't seen Postgenomic yet, it's definitely worth a look - front page notes it "collects data from hundreds of science blogs and then does useful and interesting things with it." It pulls together commentary on different topics, issues, and recently published papers.