Web design vocabulary refresh (Design Shack)
Pea.rsis a free open source WordPress theme which helps you set up your own pattern library (for HTML and CSS patterns). By Dan Cederholm (who made Dribbble)
Initializr Start an responsive HTML5 project in 15 seconds via @brad_frost
A beginners guide to HTML and CSS via @SmashingMag (edit: By Code Academy instructor Shay Howe, HT codeacademy.org)
“Look up HTML5, CSS3 features, know if they are ready for use, and if so find out to use them – with polyfills, fallbacks or as is”
The Expressive Web - Awesome HTML5 / CSS3 site from Adobe with examples, tutorials and more.
20 HTML5 sites that changed the game in 2011
W3C Love Validate the HTML markup of a whole website in one click (you can only check one page at a time with the official W3C validator).
HTML5 CSS3 Advent calendar with pro tips
http://movethewebforward.org/ by Paul Irish and co. It’s a new site to help developers “level up” and contribute to the internet. Also see the epic flame war comments between Paul Irish and Jeffery Zeldman
TeamTreeHouse: Learn how to make the internet
Watch videos, take tests, earn badges, launch your startup.
Trend: The gamification of Education (and everything really). Think Codecademy.
Pretty sweet responsive site as well.