Sitecake - Drag and drop CMS for HTML websites. It's flat file CMS so it's pretty fast.
Atomize by Quarkly - Library for creating atomic react components
Anchor CMS - Free and lightweight blogging system
Bulma - Bulma is an open source CSS framework based on Flexbox and built with Sass. It's 100% responsive, fully modular, and available for free.
Textpattern - Textpattern is an elegant content management system that is free, open source software.
Circle.so - Bring together your discussions, memberships, and content. Integrate a thriving community wherever your audience is, all under your own brand.