If you're as big of a fan of the DokuWiki wiki software as Norbert Mocsnik, you'll be very happy to check out his latest post on his blog about setting up the simple form of authentication in the application.
In my opinion DokuWiki is the best wiki software out there (see features). In addition to all those cool features like namespaces, it stores pages in plaintext files, thus no database backend is required. Setting it up is pretty easy also. I promised to investigate the steps needed to set up DokuWiki with the simplest authentication scheme for a friend and I thought others might benefit from it too, so here it is.
He starts from, well, the beginning - grabbing the latest DokuWiki download, copying it over and running through the installation and configuration. Then it's on to the web inferface, changing the Access Controls to allow for more of a fine tuning on who can do what.