Wikis can be very dynamic web sites if there are enough interested people. If you have just a few people involved, it becomes more like an easy documentation tool.
Check out http://kehei.com for an authenticated wiki written in perl.
Check out http://wiki.2gn.com for another one written in PHP.
The problem with authenticated wikis (in my experience) is that there is rarely a critical mass of users to make the content really dynamic.