HTML5 Doctor - Helping you implement HTML5 today.
The HTML5 Test - Find out which parts of HTML5 are already supported by your browser today and compare the results with other browsers.
Initializr - Initializr is an HTML5 templates generator to help you getting started with a new project based on HTML5 Boilerplate. It generates for you a clean customizable template with just what you need to start.
CSS3 Generator - Border Radius, Box Shadow, Text Shadow , RGBA, @Font Face, Multiple Columns, Box Resize, Box Sizing, Outline, Transitions, Transform, Selectors and Gradients.
CSS Patterns Gallery - The patterns themselves should work on Firefox 3.6+, Chrome, Safari 5.1, Opera 11.10+ and IE10+.
Prefix My CSS - Prefix your CSS3 code. Instantly!