I find LiveMocha particularly interesting for their use of crowdsourcing --- which has evolved quite a bit since I joined. Basically, they have generic course templates in English, and then give people "MochaPoints" (which as far as I can tell are completely useless) for translating the course into their own language, or making recordings of phrases, or even just evaluation others' translations. And of course, MochaPoints are prominently displayed on every profile, making you aware of the pecking order and incentivising you to increase your own points.<p>This isn't a perfect approach (it's heavily biased towards people who like learning by memorising phrases, rather than people who like learning by picking apart sentences through detailed study of grammar --- I don't think crowdsourcing explanations of grammatical points will ever bring satisfactory results, anyway), but it works well for people who like it.