For those who don't know: a wiki is a web app for collaboration; all users can edit the web pages, add links/images/etc. It uses a simple markup language similar to html or UBB codes.
See
http://en.wikipedia.org/wiki/Wiki
There are a zillion varieties of wiki, but in general you need to be able to install and run CGI scripts on a webserver. After that, you configure, generate a few starter pages, and (in theory) the users do the rest (adding pages and links). Disclaimer: I've read a lot about wikis and plan to use one at work in the future, but I've never set one up.
Advantages: once set up, everybody can pitch in on generating and organizing content; all content in one place
Disadvantages: someone needs to set it up & host it; users need to learn to use it (far easier than learning to play dom2...)