I thought I would post a few really helpful html 5 examples and test pages.
A good page to keep track of is http://www.w3.org/html/planet/
Drag and Drop (works in firefox 3.5)
http://decafbad.com/2009/07/drag-and-drop/api-demos.html
Test Elements
This is a layout which uses the new header, nav, aside and footer elements to build a page as well as a few other new HTML 5 tags.
http://www.brucelawson.co.uk/tests/html5-elements.html
Layouts Tutorial
Another HTML 5 layout but as a tutorial.
http://net.tutsplus.com/tutorials/html-css-techniques/html-5-and-css-3-the-techniques-youll-soon-be-using/
Building an XHTML5 document
http://www.hagenburger.net/2009/03/html5-xhtml5-with-css-for-safari-firefox-opera-ie
Enjoy checking out html 5