Someone steal this idea: A site with screencasts of people writing software in the editor of their choice. Let people browse videos by editor, programming language, whatever else.
Peeepcode has a "Meet Emacs" screencast available for about $9 as well here: https://peepcode.com/products/meet-emacs
It's not quite the site you describe, but I've learned quite a bit watching Vimcasts.
Also, PeepCode released "Smash Into VIM" yesterday: http://peepcode.com/products/smash-into-vim-i