concrete5 CMS is a free open source content management system.
It's a software to install on a web server, and manage web contents via web browser. concrete5 has very intuitive interface and very easy-to-use. And it is very easy to design an original theme as long as you know HTML and CSS.
For more information about concrete5, visit their web site.
About concrete5 Japan Users Group
concrete5 Japan Users Group is a Japanese open source software group of volunteers from programmers, web developers, designers to the people who are doing web design as a hobby.
Also we are always looking for new members who can speak both English and Japanese to help us translate. Please contact us.