TinyCMS
TinyCMS is an open source, lightweight PHP CMS script.
WonderCMS
WonderCMS is the smallest flat file CMS (does not require a database). Editing content is easy – clicking anywhere in your admin panel will enable you to edit any content you see.
Quick.Cms
Easy to modify and to use content management system. CMS is incredibly fast and easy to install.
gpEasy CMS
gpEasy is much more than just an easy to use content management system. It’s full of features to help you build and maintain rich websites. And since it’s open-source, it will always be free!
GetSimple CMS
The Simplest Content Management System. Ever. GetSimple has everything your client needs, and nothing a CMS doesn’t