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.
DokuWiki - DokuWiki is a simple to use and highly versatile Open Source wiki software that doesn't require a database.
Milligram - A minimalist CSS framework
Wiki.js - An open source, modern and powerful wiki app built on Node.js, Git, and Markdown.
Material UI - A CSS Framework and a Set of React Components that Implement Google's Material Design
TiddlyWiki - a non-linear personal web notebook