I briefly mentioned Engkoo a while back and just now spotted some additional info about it on Microsoft PressPass including a nice Silverlight demo to watch.

Teach someone a word and help them once. But teach a search engine linguistics, and it can help people learn an entire language

According to statistics, about 15 new words and uses for words appear in the English language every day,” says Ming Zhou, senior researcher and research manager of the Natural Language Processing Group at Microsoft Research in Beijing. “Any manual effort will have a hard time keeping up. And translation quality has always been a big issue, so you can imagine the enormous translation potential of using a variety of data from the Web.”

(my bolding)

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Microsoft Engkoo Helps Teach English to Chinese Internet Users: Engkoo, a new language assistance search technology released by Bing in China, helps Chinese speakers learn not just English words but the language itself, complete with slang and idioms.