WordPress - WordPress is web software you can use to create a beautiful website or blog. We like to say that WordPress is both free and priceless at the same time.
Sitecake - Drag and drop CMS for HTML websites. It's flat file CMS so it's pretty fast.
Craft CMS - Content management system built on Yii PHP Framework
Anchor CMS - Free and lightweight blogging system
HubSpot Website Platform - HubSpot Website Platform is a content management system that enables marketers to build websites personalized for every visitor.
Textpattern - Textpattern is an elegant content management system that is free, open source software.