Flux CMS is a XML/XSLT CMS based on PHP 5 (http://www.php.net/) and Popoon 
(http://popoon.org/). It's easy to use for the enduser and has WYSIWYG editing
capabilites, but it's also very extensible and powerful for implementors to 
suit your needs.

WWW: http://www.flux-cms.org/