Bootstrap - Simple and flexible HTML, CSS, and JS for popular UI components and interactions
CSS Blocks - Blazing fast CSS for your design systems and app components.
Elastic UI - React-based design library made for use with Elastic products
React Router - React Router is a routing for React.js, that synchronizes the components of application with the URL & supports server side rendering.
Semantic UI - A UI Component library implemented using a set of specifications designed around natural language
Storybook - Storybook is an open source tool for developing UI components in isolation for React, Vue, and Angular. It makes building stunning UIs organized and efficient.