One of my first screen casts was an HTML5 primer (http://nobulb.com/2009/11/html-5-primer/). I also found a really good slideshow on what's new in HTML5 (http://slides.html5rocks.com/).

(Not certain that the quality of information in my screen cast is nearly on par with the other info presented here, but it was a crowning achievement and something I'm proud of. Let me know if this is bad form, I'll remove this comment.)