Galen Framework : Automated testing of look and feel for your responsive websites.
Layout testing seemed always a complex task. Galen Framework offers a simple solution...
lit : a ridiculously small responsive css framework
Foundation : An easy to use, powerful, and flexible framework for building prototypes and production code on any kind of device.
enquire.js : A lightweight, pure JavaScript library for responding to CSS media queries.
Sprite Cow : Sprite Cow helps you get the background-position, width and height of sprites within a spritesheet as a nice bit of copyable css.