semiCMS
SemiCMS is a XHTML-compliant content management system that I made for providing my customers with an easy to maintain, highly customizable and powerful solution for bringing content to the web. As I have put quite a lot of work into it by now, it is now ready for rolling out to customers.
Currently, there are no plans of selling semiCMS as a stand-alone product and this will probably not change in the near future, so the only way of getting a semiCMS-driven site at the moment is to ask me to be your webmaster 
Requirements
semiCMS has all the "classic" PHP content management requirements: A webserver, PHP (both version 4 and 5 supported) and a MySQL server. If you want to have mod_rewrite support, it would also be a good thing to have Apache as your webserver and the mod_rewrite plugin installed.Technology
On the frontend, semiCMS tries to stay back as much as possible, letting the authors of the page and the design determine about every byte of HTML output. This means that as long as both your design and content are XHTML strict compliant, semiCMS-served pages should be XHTML strict-compliant, too.
Tip: Try browsing this site with lynx, it's fun!
In the backend, semiCMS still tries to be standards compliant, but makes heavy use of AJAX technology provided by script.aculo.us and the prototype framework to make editing as fast, convenient and intuitive as possible. The beautiful icons in the program come from the famfamfam.com silk icon set.
Demo video
As there are no current plans for selling semiCMS, I have no live demo avaliable for the content management system, but feel free to watch this video showing some of the features in semiCMS:
