After years of only talk about the HTML5 specification the last 2 years or so browser vendors are finally starting to implement most parts of the specification, even though the HTML5 specification isn’t completed yet. Because of this I haven’t been paying much (or any) attention to it at all so I’ve got no clue about all the new features that HTML5 brings.
Luckily for me the free online book Dive Into HTML5 by Mark Pilgrim gives a nice introduction to HTML5. It gives a nice explanation on how to use <article>, <header>, <footer> and <nav> but also some of the other elements as <video> and <canvas>. Geo-location, storage, offline availability, new types of form elements and microdata have chapters of their own as well. I think microdata is an interesting addition, although I’m not sure yet it would serve any other purpose than providing specific data to search engines.
Reading this book has brought me up-to-date quickly on the HTML5 topic and makes it a less scary beast for me. If you’re interested at all in web development then I suggest reading Mark Pilgrim’s excellent book.
Edit: I was told the site no longer exists, but https://digital.com/tools/html-cheatsheet/ has a nice overview as well.