Ed Summers has done some nice analysis of the top hosts referenced in article space, based on SQL dumps: http://inkdroid.org/journal/2010/08/25/top-hosts-referenced-in-wikipedia-par...
People with more in-depth knowledge might make something of this -- for instance the importance of bots in external links, or the prevalence of certain types of information.
For instance, why/where/how is edwardbetts.com used? (doesn't seem to be postcode data, which was my first guess)
See also his linkypedia code: http://github.com/edsu/linkypedia
-Jodi