Groundwork A barebones collection of stylesheets that can be used to get you up and running as fast as possible. CSS
Fbootstrapp A toolkit designed to kickstart development of facebook iframe apps in both relevant sizes. HTML Tools
Yeoman A set of tools, libraries, and a workflow that can help developers quickly build web apps. Tools
Brackets An open-source editor for development built on top of web technologies such as HTML, CSS and JavaScript. CSS HTML Javascript Tools
Brunch An assembler for HTML5 applications. It‘s agnostic to frameworks, libraries, programming, stylesheet... HTML Tools
Clearless A reuseable collection of carefully-considered Less mixins, or YALML (Yet Another Less Mixin Library). CSS LESS
Bourbon A library of Sass mixins that are designed to be simple and easy to use. No configuration required. CSS SASS