Here is a list of popular CMS built with Ruby on Rails
1. Camaleon CMS is an advanced and dynamic Content Management System Based on Ruby on Rails 4 which is an alternative to Wordpress in Ruby on Rails. This CMS can be adapted to any kind of project without programming and giving to users more time for the content instead of programing.
2. Radiant CMS
Radiant is a no-fluff, open source content management system designed for small teams. Radiant features:
An elegant user interface
Flexible templating with layouts, snippets, page parts, and a custom tagging language
A first-class extension/plugin system
Simple user management and permissions
3. Refinery CMS is perfect for creating custom content manageable websites. We use "The Rails Way" where possible so you have to learn as little as possible to get started!
4. Locomotive CMS is completely Open Source. It's a free software released under the MIT license. Use is as you like. Copy it, modify it, tweak it and resell it. You're free to use it however you like, as long as the copyright notices remain in tact.