www.postgenomic.com

... is a very interesting new site, currently in beta version that aggregates life science blogs and then analyses that data. It seems to me to be a cross between a citation tracker, impact factor analysis tool, and search engine.
From the website: "For example, it allows you to get an instant picture of which web sites are being heavily linked to by researchers in the medical sciences, or which papers are being cited or reviewed most often by bioinformaticians, or which buzzwords are being used the most frequently by evolutionary biologists". (http://www.postgenomic.com/)
Perhaps this could be useful information for scientists interested in entering the blogosphere as it shows which domains and which journals bloggers are linking to most frequently already.