I'm fascinated by all of the discussions and research that is going on in the weblog world about the interconnections between people and the communities of interest and/or practice that seem to naturally form.
One interesting project in this area is the NITLE Blog Census, this site has an entire database of weblogs that can be downloaded and used for research. Another database that might be useful is Journal Citation Reports.
I was prompted to include the journal citations as an example of prior art because of an entry at Thoughts Arguments and Rants about academic tenure. Brian Weatherson focuses on the most influential philosophy journals and reaches the conclusion that there are not nearly enough quality publication slots available to allow even a majority of professional philosophers to be published regularly. I don't have the expertise to judge his numbers but the question of deciding on what makes a journal 'influential' seems to parallel the question of what makes the a-list in blogland.