Since this article inspired me to look into getting Wiki'd on the Mac, but is now starting to "show its age," I thought I'd mention an easy to configure Wiki I got up and running in about 10 minutes.
PmWiki (http://www.pmwiki.org/wiki/PmWiki/PmWiki) is very easy to get up and running. It uses PHP, but does not require SQL.
The outline of the steps I took were:
Preferences:Sharing --> start Personal Web Sharing
Got PHP running with a few commands borrowed from the installation instructions of the excellent Andromeda music streamer:
cd /etc/httpd sudo apxs -e -a -n php4 libexec/httpd/libphp4.so
Installed PmWiki per their installation instructions; in brief:
downloaded the latest pmwiki code, extracted it, renamed the directory to 'pmwiki'; moved it into the webserver folder
moved into the webserver's document tree. Ran 'chmod 2777 .' in the directory containing pmwiki.php to temporarily grant extra permissions
loaded pmwiki.php from a browser (it creates the database folder)
ran 'chmod 755 .' in the same directory to restore permissions
Up and running in less than 10 minutes. Didn't have to install / configure SQL. (Or Ruby, which would have been needed for Instiki.)