Esperanto or Swahili
Started conversation Feb 11, 2009
A much older and more successful international language than Esperanto is Swahili, which enabled speakers of Arabic and various East African tribal languages to communicate with each other and is now widely spoken throughout East Africa. As I don't speak either, I can't comment on their relative ease of learning, but Esperanto does seem to be a bit like re-inventing the wheel.
A different approach would be to learn to read Chinese - a written language which is equally comprehensible to the speakers of the many different languages which exist in China.