You should have run across the doctors site... it's run by "doctors" which are mostly people who are actively working on the HTML5 spec themselves. (every so often, they get mail from people thinking it's a medical site... and Bruce will sometimes post the hilarious descriptions of puss-filled sores or other bodily complaints for the lawlz...)
You might also want to check out Bruce Lawson's blog, even tho it's private: Bruce Lawson’s personal site : HTML5
Yeah, that's right, he's riding a unicorn fighting Nazis with the power of HTML5 and a "lazer" gun. Yup.
If your CSS is good, learning some CSS3 junk from any decent tutorial site should be fine.
HTML5 you need to be a bit more discerning about. Resources from Opera, Mozilla or Chrome guys (like Paul Irish) should be pretty safe. The important thing to remember about HTML5 is it's in Draft. That means anything, even <header> tags and stuff, can change at any time (even though obviously some of it is less likely to change than others... there are "more stable" areas and "actively contested" areas).
Also be aware there is a growing split between the WHATWG version of the specs and the W3C version... mostly they split on the newly-announced Schema.org plan (vs W3C's RFDa plan) and accessibility stuff (which isn't a big deal really... if you care about accessibility and want to follow "the spec" you can just follow W3C for now and even if a lot of stuff ends up being left out of the WHATWG version, you as an author should always be free to add it in anyway).