Hyperform is a complete implementation of the HTML 5 form validation API in Javascript. It replaces or polyfills the browser’s native methods and eases your validation task with custom events and hooks.
Shumway is an HTML5 technology experiment that explores building a faithful and efficient renderer for the SWF file format without native code assistance.
An HTML5 Presentation Editor. A GUI / Authoring Tool for ImpressJS and Bespoke.js
Source at https://github.com/tantaman/Strut
2D+3D game making for indies
Able Player is a fully accessible cross-browser media player. It uses the HTML5 <audio> or <video> element for browsers that support them, and (optionally) the JW Player as a fallback for those that don’t.
A game in the address bar using html5 history.replaceState
HTML5 compatibility on mobile and tablet browsers with testing on real devices
JavaScript Application Framework
manifestR is a bookmarklet, which you drag to your bookmarks bar. Then, when you visit any page, you can click the manifestR button, and it will create an HTML5 appcache manifest file for that page.
HTML5 Webcam for your website
an open source rich text editor based on HTML5 technology and the progressive-enhancement approach.