I found the last two especially interesting.
Also, with https://github.com/kripken/emscripten you can run a "port" quite a bunch of apps to JavaScript.
And don't forget you can decode several audio codecs: http://labs.official.fm/codecs/ and video codecs: https://github.com/mbebenita/Broadway + http://people.xiph.org/~bens/route9/route9.html
I found the last two especially interesting.