If you've got php working on your server a great wiki choice is PmWiki.
You can check it out at http://www.pmichaud.com/wiki/PmWiki/PmWiki
The basic setup is very easy. I relies on a flat text database so you
needn't worry about having to setup MySql or some other fullblown
database system. It's got a lot of additional features beyond the basic
setup. (See the PmWiki Cookbook
<http://www.pmichaud.com/wiki/Cookbook/HomePage> section at the url
above.) It's under active development and there's very friendly,
helpful listserv support.
An excellent working example of PmWiki is here:
USC Aiken Library