WordPress.
Teaching you the world's leading Content Management System is what I am crazy about. Working with it and helping others use it is what drives me.
Why?
WordPress is something most of us can master. It's free, open source software that has a huge developer community that is ready to help me and you. And you don't need to be a coding nerd to really do fantastic things with it (but code knowledge is always a good thing).
Look at it this way. Not that long ago a web site that would have bend cost prohibitive for small businesses can now be built and maintained for pennies on the dollar! What a bargain and it gets better all the time.
I've been teaching HTML, CSS and WordPress for a very long time.
I do WordPress training via private webinars:
http://joyofwp.com/private-webinars/
and in a Group Webinars:
http://joyofwp.com/group-wordpress-webinars/
I'm on the faculties of Pratt Institute and the Fashion Institute of Technology in New York City. I teach web design in class and online for their students.
I have had the privilege of teaching over 1000 people from over 60 countries the primary skills needed to design for the web be they HTML, CSS and/or WordPress.