320 and up : ‘320 and Up’ is a lightweight, easy to use and content first responsive web design boilerplate.
Onsen : Open source HTML5 hybrid app framework for PhoneGap & Cordova
Mobile-optimized HTML5, CSS and JavaScript with Web components
Responsive layout, Materi...
Sizzy : A tool for developing responsive websites crazy-fast.
Open sourced : https://github.com/kitze/sizzy
Mobello : Mobello is high performance javascript UI framework for HTML5 mobile app
Screenfly : Test Your Website at Different Screen Resolutions
HTML5 Boilerplate helps you build fast, robust, and adaptable web apps or sites. Kick-start your project with the combined knowledge and effort of 100s of developers, all in one little package.