For quite a while we have been looking into approaches to building mobile first responsive pages. Our current site uses Jquery UI which has been useful for some aspects of the design of the site. We wanted something a bit more prescriptive that provided a framework for us to move to creating awesome page that deliver a mobile app style experience inside a web page.
Enter Foundation from Zurb
On a recent project that I am managing I was fortunate enough to be able to work with Hanno, who use Foundation extensively to allow rapid prototyping. It seemed out search for a framework was over!
The grid approach used in foundation makes layout a synch. The block grid is also get for creating fluid layouts that adapt for different device sizes. The bottom line is that the guys at zurb have simplified the detection of small, medium and large device formats as well as orientation! On top of that there are exclusions and inheritance. The concept is design for small first and override for large formats. Combined with size dependent grids you can achieve what ever you like with minimal markup.