SilverStripe is a Content Management the way it was meant to be. It is powerful enough for any website or intranet design and simple enough for anyone to use with the following main features.

• Simple. Intuitive and user-friendly
• Flexible coding framework (MVC)
• Scalable. From 1 page to a million
• Fast. As responsive as a desktop app thanks to native Ajax support
• Standards Compliant. Fully XHTML compliant
• Modular. Easy to extend
• Template Freedom. No restrictions on the look and feel of your site
• Open source. It’s free (BSD) and you can contribute to the project.
• Cross platform (Windows/Linux/Mac) and easy to install (PHP based)

Pricing: Free
Source: http://www.silverstripe.com/