Apple’s page on HTML5 and Web Standards as supported by their Safari 5 web browser.
Lots of background information and examples related to the various modules that make up CSS3.
Provides royalty-free fonts in various formats suitable for distribution on the web.
The actual HTML5 specification at the W3C
Mozilla Developer Center’s page on HTML5.
How to write websocket servers with Node.js.
Demonstrations of HTML5 (and related) features in Internet Explorer 9
Information on em-websocket, a Ruby library for building web socket servers.
Contains a detailed description of Flash Socket Policy files.
Discussion of font stacks, with some excellent examples.
Information on HTML5 video, with code to play video on all browsers.
Browser compatibility tables for HTML5, CSS3, and related technologies.