CMSs to Try

Quick.Cms
http://opensolution.org/quick.cms,en,10.html

gpEasy
http://gpeasy.com/

AutoCMS
http://www.autocms.org/

10+ Simple and Lightweight but Powerful and Free CMS Solutions
http://www.narga.net/10-simple-and-lightweight-but-powerful-and-free-cms-solutions/

S40
http://s40.biz/

Pulse CMS
http://pulsecms.com/

...

The big thing is the format of the data files, and accessibility from
outside the CMS.