Archives Wiki is an example of a wiki maintained by a professional association.
Archives Wiki is sponsored by the American Historical Association. It is intended to be a clearinghouse of information about archival resources throughout the world. While it is primarily designed to be useful to historians and others doing historical research, we hope that researchers in many disciplines will find it useful.
Notable qualities that distinguish this wiki from the equivalent sort of effort within Wikipedia include:
All contributors must log in, and are expected to use their real names and make a link to some biographical information about themselves. This adds to the idea that the people contributing to the site are professionals. Contributor guidelines make it clear what the expectations are, and the people adding in information look like they are primarily archives people and not wiki people.
Unlike some free hosted wikis, there is no advertising visible. The sponsorship of the AHA pays for the system. This means most importantly that there are no inappropriate ads - the occasional Dungeons and Dragons ads or World of Warcraft ads that decorate free hosted sites, or the weird Google Adwords ads that show up from time to time.
The wiki itself has a definite structure, with a design that makes it obvious where to add pages around the globe (by state and country), and with a template that you are expected to follow when adding a new entry. Many wikis are freeform and chaotic; this one doesn't feel that way.
The "recent changes" part of a wiki is an indication of signs of life in a system; how many people are contributing on a regular basis, and what are they adding in? Archives wiki has about a dozen pages in the last week added to, and they are reasonably complete on observation - the site has quite a bit of variety in depth, but some of the pages are very clearly very complete and useful.
The hardest thing about wikis like this one are that they are very clearly a global effort, requiring both knowledge by people around the world and the capability to do something that needs ongoing maintenance. There's some "contributors to pages" ratio that needs to be right so that enough people care enough that it stays accurate enough. As a model, though, of a directory style wiki maintained by a professional association it's a good one.