There are no CMS in the SliTaz 3 repository, but you can find drupal in cooking. The latter is probably proof that we're slowly starting to package PHP CMSes.

But for now, nothing is stopping you from installing it yourself. From personal experience, it seems to run well if you have MySQL, Lighttpd and php-cgi installed and properly configured. It actually runs faster on Lighttpd than it does on Apache2 if you can believe that ^.^