Dokuwiki is an efficient, powerful, full-featured and at the same time lightweight wiki which could be also used as a small CMS. It offers a high degree of customizability, that is very easy for who already knows PHP. It has an elegant readable syntax and stores the pages straight on the filesystem as simple .txt files.
1. Download the latest version from http://www.splitbrain.org/projects/dokuwiki
2. Decompress it in a web server directory
3. Open /path/to/dokuwiki/conf/dokuwiki.conf and customize the settings, at least the title
4. Create changelog:
5. Make the whole data directory writable:
chmod -R 0777 /path/to/dokuwiki/data
6. All done. The wiki is at its default settings very open, with public access everywhere. If you wish to make some sections private, you should configure users and ACL. To make some pages read-only, it is enough to set them read-only on the filesystem!