Non standard sources
- Mozilla’s MDN: an open wiki with highly recommended content. Huge amount of content, examples, depth and implementation status. Their HTML5 front page beautifully summarizes the main themes on HTML5: https://developer.mozilla.org/en/docs/web/Guide/HTML/HTML5
- Web Platform Docs WPD: wiki with tutorials
- CSS Tricks: amazing CSS source. Create and maintained by Chris Coyier http://chriscoyier.net/, now has articles by many. Very high quality techniques. Closed source apparently.
- w3schools fine for beginners, but not open source, and thus cannot update fast enough, so may contain errors and has been criticized by many devs. Tutorials are a bit shallow. Insane Google rank, which makes may devs mad.
- HTML5 Doctor: similar to HTML5 rocks, but 6 guys from famous web related companies. Lots of examples.
Implementation status trackers
- All modernizr tests, cross referenced to Can I use.
- Can I use.
- kangax compatibility table.
- HTML and CSS: https://github.com/mdo/code-guide
- HTML5 demos: many small examples, which is basically my approach in this repository
- https://code.google.com/p/browsersec/wiki/Main, by a Google employee