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 : The HTML5 Shiv enables use of HTML5 sectioning elements in legacy Internet Explorer and provides basic HTML5 styling for Internet Explorer 6-9, Safari...
Flowplayer : Flowplayer is a beautiful and minimalistic, yet full-featured HTML5 video player that lets your video be the star of the show. Supports all devices.
flv.js : An HTML5 Flash Video (FLV) Player written in pure JavaScript without Flash. LONG LIVE FLV!
Shumway is an HTML5 technology experiment that explores building a faithful and efficient renderer for the SWF file format without native code assistance.