Concrete5

Concrete5 is an open source content management system (CMS) for publishing content on the World Wide Web and intranets. concrete5 is an amazing way to manage the content on a website. It provides a robust framework for adding interactive functionality; in no way is concrete5 “light weight”. But it might not be the best choice to build the next Twitter.com or a secure banking app from scratch. The eCommerce add-on for concrete5 is super flexible and you can build online stores that few other systems can support.
FEATURES

Automatic add-on & theme installation
Integrated help system with commercial support options
File manager with bulk upload and image manipulation
Opensource
Chat Module
e-Commerce
WYSIWYG text editor
Full Caching
Flexible meta data
Content scheduling
Integrated spellchecker
An open marketplace of add-ons
Easy Google Analytics integration
In-context editing toolbar
Automatic navigationsTrack versions