sathotwords.com
Software stack
Frontend: HTML, CSS, JS(+jQuery) (and a bit of FlatUI styling)
Backend: Python script hosted on Appfog, Firebase
Hosting(and some workarounds):
Both the front-end and python script are hosted on Appfog, which has been a really great platform up to now. Their 'free' tier is amazing (2GB Ram). To host the static front-end(HTML,CSS,JS), I had to pretend it was a PHP application as their is no option for this on Appfog. For the python script, I required a few dependencies and Appfog doesn't currently install dependencies for standalone python app (they are working on it apparently). The work around wasn't too complicated, implementing it as a Flask based app solved the problem (requirements.txt is read if you're using a pythonic web framework).
Some thoughts
Building stuff is really the best way to learn a language and it's features. I cannot stress this enough, it's so satisfying to write something yourself and see it work.
I'm actually quite proud of my little script(roughly 200 loc), there are a few neat little gems in it that I was particularly proud of (recursion, always makes me smile).
Why did I choose Appfog instead of [insert cloud hosting company]? They are generous with their free tier, as a 16/17 year old that's important, plus it's actually really awesome.
How's Firebase? Firebase is great, using it as a database replacement here and it's actually easier to integrate than a proper database (of course there are differences, Firebase just happened to be a good match for this). You should check that out also.
I firmly believe that education should be as cheap and as open as possible (I fully support, admire and use Khan Academy).
Are you a startup/company in London
http://pastebin.com/jLXwkZh0