I quite like Duolingo at the start. They did an excellent technical presentation at one of the AWS events I attended, and I think they were doing some really i

I quite like Duolingo at the start. They did an excellent technical presentation at one of the AWS events I attended, and I think they were doing some really innovative stuff. If I recall correctly, their original model was to have more advanced learners crowdsourcing translation services, similar to how CAPTCHA made money. I guess the problem with that model is not many people become advanced learners. Something has to support all of the free install, use for a week or two crowd, and I guess that's where the hearts system came in. Either way, they never supported the language I had to learn (Icelandic, few do) so I found another app/site that did.