Dokuwiki is the wiki you are using right now. There's potential it will work for multiple instances, but I haven't tried it.

  * aptitude install dokuwiki, php5-cgi and nginx
  * /etc/dokuwiki/local.php configured to rely on DOCUMENT_ROOT, so can be 
  * /etc/nginx/sites-available/wormnet configured to use /srv/wormnet/wiki