A side project of mine with fellow Clearleftie Trys Mudford, "Utopia" encourages designers and developers to share a systematic approach to fluidity in responsive design. Instead of designing for x number of arbitrary breakpoints, we can design a system within which elements scale proportionally and fluidly.
utopia.fyi is where we pull our thoughts together, show working examples, and host free tools to support designers and developers who are interested in working this way.