Response JS is a lightweight, jQuery plugin, that gives designers/devs tools for producing performance-optimized, mobile-first responsive websites. It provides easy-to-use action hooks for dynamically swapping code blocks based on screen sizes and semantic methods for progressively serving images/media via HTML5 data attributes. Response's methods are also available as object properties, making them useful tools in OOP-minded custom development.
Full documentation is in the works. (~November) There are a few examples in the source and here.
Latest version: 0.2.7 | min | Github
Developer: Ryan Van Etten | Twitter | GitHub