To make a RWD site I'm having to rewrite a lot of the framework to be mixins instead of classes so that I can use them in @media as SASS doesn't allow @extend in @media any more[1]. What I'd find really useful would be a framework thats entirely built from mixins/partials and outputs no css until you create your own classes that use them.
[1]: https://github.com/nex3/sass/issues/154 Disallow @extend within directives
Here's exactly what you're looking for:
* Bourbon: A mixin library for Sass (http://bourbon.io/docs/) * Neat: A semantic grid framework built on top of Sass and Bourbon (http://neat.bourbon.io/)
And, if you use LESS, you have these options:
* LESS Elements: Mixins library for LESS (http://lesselements.com/) * Semantic.gs: Semantic CSS grid system for LESS (http://semantic.gs/)