A Beginner's Guide to HTML & CSS is a nice resource developed by Shay Howe whose resume reveals that he works on the user interface for Groupon among other projects. There are currently ten text-based lessons for beginners. Once you've mastered the beginner lessons you can try your hand at the advanced lessons. Three advanced lessons are currently available and seven more are slated for publication between now and March 4, 2013. And according to this Tweet from Shay Howe, a print version of these lessons may be available in the future.
Applications for Education
Using a WYSIWYG
platform like Blogger or Google Sites to create a blog or website is
more than adequate for most teachers and students. But at some point you
might want to beyond the limitations of WYSIWYG. It's then that you'll
want know how to write and edit HTML yourself. A Beginner's Guide to HTML & CSS could be a good way for you and your students to learn together.
H/T to Lifehacker.