The structure of wikis is interesting. How are the page inter-linked? There is an example in http://seattlewireless.net/index.cgi/HowDoesThisWikiLookLike. The number of links per page (references to other pages or references from other pages) seems to follow a PowerLaw distribution.
There are more examples (in French) on http://reseaucitoyen.be/index.php?TopologieDuWiki.
The 29th of August 2002, SeattleWireless looked like  :
with the references counts distribution like this :
raw data is in  and a zoomable graph in  (29aug2002).
See also HowDoesThisWikiLook, TouchGraph, TouchGraphWikiBrowser