HTML5Rocks.com is an open source project!. HTML5Rocks.com A resource for developers looking to put HTML5 to use today, including information on specific features and when to use them in your apps. Google have recently updated their HTML5ROCKS site, originally launched in June this year, with numerous new demos and tutorials for HTML5 and CSS3. The HTML5ROCKS Code Playground offers various interactive demos, along with code snippets, for various new CSS3 features including: You can visit the site here.

• Multicolumn Layout
• Rounded Corners
• Web Fonts
• Text Wrapping
• Text Stroke
• Transitions
• 2d Transforms
• Animations
• Gradients
• Selectors

And you can find other HTML5 resources

• HTML5 Readiness – visual timeline of HTML5 feature support.
• Dive into HTML5 – learn HTML5 and have fun reading a book at the same time.
• Modernizr – JavaScript library for feature detection and control fallback cases of HTML5.