MoinX is a Mac OS X desktop wiki.
MoinX gives you a full blown and unmodified MoinMoin wiki without forcing you to run a full blown web server. Instead MoinX is bundled with the high performance Twisted webserver.
It can run as a private wiki, available only on your computer, or it can be set up as a public wiki available over your local network. It also can take advantage of Apple's Bonjour/Zero Configuration networking, so that a MoinX wiki configured on a teacher's computer can be set up to be automatically seen by students using the Safari or Camino browsers (both support Bonjour), or from within Internet Explorer and Windows using Bonjour for Windows.
For the past two years some teachers in my school have been using Instiki, another lightweight desktop wiki, in a similar fashion. The classroom wiki space is installed on the teacher's laptop and is available discoverable from anywhere on our network. Students can access and create pages and complete assignments using the web browser and wiki interface. As I have written before, we find this implementation of a wiki to be very easy for both our teachers and students to understand and utilize.