xCSS : xCSS bases on CSS and empowers a straightforward and object-oriented workflow when developing complex style cascades.
Milligram : Milligram provides a minimal setup of styles for a fast and clean starting point. Just it! Only 2kb gzipped! It's not about a UI framework. Specially ...
UIkit : A lightweight and modular front-end framework
for developing fast and powerful web interfaces.
YAML : A modular CSS framework for truly flexible, accessible and responsive websites
YAML Builder : A tool for visual layout development of YAML based CSS layouts
