I've tried out a lot of CMS lately. Joomla, Drupal, CMSMadeSimple. Joomla and Drupal are too complicated for the small sites I want to use them on, even CMSMadeSimple which is by far the most simple (clever name eh?) is a bit too much.
I recently came across CushyCMS and it is a pleasure to work with so far. It is simple and easy to use and gives you all the functionality you need for small sites. The free option is so good, I'm tempted to go for the Pro version!
I would definitely recommend it for simple XHTML / CSS Sites