I have used a cms created by interactivetools.com called page publisher and really like it. Here is a link to the site http://www.interactivetools.com/products/pagepublisher/ . It is Perl / CGI based and they encourage developers to brand the cms to your own benefit. You can place an editable area anywhere you choose. It utilizes a WYSIWYG interface for editing a section. You can limit what is available for them to edit. It is nice for letting a client edit areas of a site without worrying about altering the design or breaking a page. Not free but definitely worth the money.
You may find something at hotscripts.com if that does not seem to fit your needs. Good luck in your search and let us know if you find something you really like not mentioned here.