polyfill : polyfill makes web development less frustrating by selectively polyfilling just what the browser needs. Use it on your own site, or as a service.
RequireJS : RequireJS is a JavaScript file and module loader. It is optimized for in-browser use, but it can be used in other JavaScript environments, like Rhino ...
Shumway : Shumway is an HTML5 technology experiment that explores building a faithful and efficient renderer for the SWF file format without native code assista...
Hyperform : Hyperform is a complete implementation of the HTML 5 form validation API in Javascript. It replaces or polyfills the browser’s native methods and ease...
The HTML5 Shiv enables use of HTML5 sectioning elements in legacy Internet Explorer and provides basic HTML5 styling for Internet Explorer 6-9, Safari 4.x (and iPhone 3.x), and Firefox 3.x.