Radiant, the minimalistic CMS for Rails
http://radiantcms.org/ Radiant CMS Features
An elegant user interface
The ability to arrange pages in a hierarchy
Flexible templating with layouts, snippets, page parts, and a custom tagging language (Radius: http://radius.rubyforge.org)
Special page-oriented plugins called behaviors
A simple user management/permissions system
Support for Markdown and Textile as well as traditional HTML (it's easy to create other filters)
Operates in two modes: dev and production depending on the URL
A caching system which expires pages every 5 minutes
Built using Ruby on Rails (which means that extending Radiant is as easy as any other Rails application)
Licensed under the MIT-License
And much more...
just run and enjoy :-)