Guest post by InfoWorld’s Peter Wayner offers a four-part series devoted to the new features of HTML5. Each articles examines the evolving spec in-depth, focusing on canvas, video, audio, and graphics for display options, including the canvas and video tags, Scalable Vector Graphics, and WebGL; local data storage, including Web Storage, Web Database, and other APIs designed to transform Web pages into local applications; data communications, for cross-document messaging, WebSockets, and other HTML5 APIs that improve website and browser interactivity; and forms, for increasing control over data input and validation.
Don’t waste your time reading that, read this: http://developers.whatwg.org/
I also like the: http://diveintohtml5.org/ and http://html5doctor.com/