Fork CMS - Home
Sitecake - Drag and drop CMS for HTML websites. It's flat file CMS so it's pretty fast.
concrete5 - An open source content management system. A point and click, free CMS that runs on a web server.
Anchor CMS - Free and lightweight blogging system
Readymag - Readymag is a design toolkit that helps create immersive digital experiences without developers in days, not weeks.
Textpattern - Textpattern is an elegant content management system that is free, open source software.