Concrete5 is a PHP open source Content Management System. During my internship at Ingram Micro Netherlands I worked on the new website of the local office. I used Concrete5 for that website so the employees there could easily update the website on their own.
For the employees that were going to use it (but also because my school required me to) I wrote an extensive documentation about the Administrative panel of the CMS. When it was finished in English (and later in Dutch) I shared it with the Concrete5 community.
I've put it on GitHub so everyone could find on a reliable location.