Over the past two years, Drupal's wiki capabilities have expanded exponentially. Yet, still we get support requests on the forums, "How can I make a wiki with Drupal?" Well, here is a detailed plan that gives wiki functionality to Drupal. This tutorial assumes you're starting with an installed version of Drupal 5.x, and that you're familiar with installing modules.
There is often this request: I want to be able to categorize my wiki pages into a hierarchy. Well, with Drupal core's book module, you can do just that! First, enable the book module. Then, go to the admin/content/types page to view your content types. Delete any content types you don't want. Then, rename the "Book page" content type to "Wiki page" or something similar. Also, in the "workflow" fieldset, make sure to check the "create new revision" checkbox. This will make it so that, by default, every edit of a page is done in a revision.