Yes, there are many content management systems available.
One I know that is most widely used is
PHP-Nuke.
Another one is
Drupal. I've gained to like Drupal a little better than PHP-Nuke, because it allows you to do a little more with your system and also has a lot of different cool "mods" you can plug-in to it.
But if you're looking for a blog type of setup, you can always go with
Word Press.