This is a great read on HTML5 happenings in 2011. As HTML5 is a somewhat vague term, I particularly liked this paragraph:
HTML5 is a semantic markup language. It actually does very little. It indicates where one paragraph ends and another begins. If all we had that was new was strict HTML5 markup, then we would have virtually nothing. After all, HTML5 doesn’t even control what a web page looks like. That honor falls to CSS. HLML5 most certainly doesn’t provide a way to program behavior - that honour falls to JavaScript. What seems to have happened is that HTML5 has become a catch-all name that means “all that new stuff”. Perhaps an even better interpretation is “all that new stuff and the extra bits that I particularly like”.