I suspect I heard about the Emacs zencoding mode from its (I believe) original author, Chris Done—he did a screencast about using Emacs for Haskell development that I found interesting, and I imagine that I found a reference while looking at his material about that.
Anyway, I created a Debian package for it, and installed it…and didn't use it for squat. Although the idea makes great sense—use a CSS-selector like language to create HTML (an idea I was first exposed to with Kris Zyp's put-selector JavaScript library)—I never even bothered to learn the keystroke to activate it.
Now, however, is the time—I'm doing some HTML writing these days, so I thought I'd go back and start learning it.
So, the magic keystroke is C-j (zencoding-expand-line)
or
C-RETURN
. The language…well, I will probably have to refer back
to the cheat-sheet on the github page now and again—it's like CSS,
without entirely being CSS—but I expect it will take a lot of the
really repetitive boilerplate out of writing HTML for me.