These are some of the sites I have found useful as I continue to learn about HTML5.
- A Book Apart - HTML5 (I have a copy of this book and consider it one of the most concise references and quick start guides I have encountered)
- http://diveintohtml5.org/ (I have a copy of this book and refer to it often.
- http://www.html5rocks.com/ (Google site covering alot of information). Don't forget to check out the interactive presentation.
- http://simon.html5.org/html5-elements (listing of HTML5 elements and attributes).