I came across this snazzy presentation on HTML 5 recently. The presentation is actually written using HTML 5, and both discusses and demonstrates some of the planned features for the new standard (note that how well it works will depend upon the browser you’re using; it worked well for me under Firefox). The first dozen slides highlight new JavaScript APIs, including the ability to store data on the client and to perform Geolocation. The rest of the presentation covers additions to HTML and CSS. Besides being nice looking, the presentation approaches the subjects exactly as I like to see: with sample code and a visual example built into each frame.
Of course, who actually knows when HTML 5 will come out and how quickly or well it’ll be adopted!