Material Design Lite
A front-end template that helps you build fast, modern mobile web apps.
Semantic UI
Semantic empowers designers and developers by creating a shared vocabulary for UI.
UIkit
UIkit, a lightweight and modular front-end framework for developing fast and powerful web interfaces.
The most advanced responsive front-end framework in the world. | Foundation
Bulma: Free, open source, and modern CSS framework based on Flexbox
Bulma is a free, open source CSS framework based on Flexbox and built with Sass. It's 100% responsive, fully modular, and available for free.