Selectize is the hybrid of a textbox and <select> box. It's jQuery based, and it has autocomplete and native-feeling keyboard navigation; useful for tagging, contact lists, etc.

Primer is GitHub's design system. This is the CSS implementation

Standards for developing consistent, flexible, and sustainable HTML and CSS.

A minimal frontend boilerplate, emphasizing workflow.

Repository for hosting the Dynamics 365 Commerce end to end sample solutions

A Sass library that helps manipulating media queries in an elegant way.