A WikiWikiWeb is a web site where anyone can edit the pages through an HTML form. Linking is done automatically on the server side; all pages are stored in a database.
This may sound rather simplistic, but a Wiki is a very unique way to collaborate on the Web. I set up a few while working at the New York Times on the Web, and the technical staff really took to them in a big way. They wrote 500 pages in just a few months (all to document the internal systems).
The addictive quality of a Wiki is that making pages is as simple as making a link to them. If they don't yet exist, the page link will be followed by a hyperlinked question mark; follow that link and you can define the new page.
With this setup, you can update and create pages from anywhere there is a web browser handy.