A software called babylon now connects their users together in a way that one can ask how to translate something. Cool but it's a software.
Bring this to the web, clean and simple interface, queue up the request by language and by newest and let users jump in to help you figure out how to pick up a girl at a bar during your trip in Italy :) Mobile app, with push... you get the idea.
Users can earn points for the good translation and maybe you could even let them record it so you know how to pronounce it. You'll get the real way to say something by real people, and even learn different ways.
Now pull all this back into a simple directory type structure to learn the essentials of each language...
You could go as far as making to top users earn points to win free flights around the world.
Monetizing could focus on travel, language learning softwares and so on... pretty easy.
That's it. That's my idea of the day.