Here's a great article from Nathan Busenitz at The Cripplegate:
John MacArthur's book "Strange Fire" is a fantastic resource on this topic. The true history of the charismatic movement has been whitewashed and glossed over until it's become almost complete fiction. Perhaps most interesting is the story of Charles F. Parham-the founder of the entire Pentecostal/charismatic movement-whom Busenitz details in his article. Parham initially believed he and his students were all speaking real languages and so they could go overseas and preach immediately without needing to learn languages the "old-fashioned" way. Until some people actually went to other countries and spoke gibberish and turned around and came home, having communicated (and converted) no one. Here's newspaper from May 31, 1901 where Parham is boasting of their newfound ability:
After it became painfully clear that none of his followers were speaking real words, Parham changed his beliefs to fit the situation-he invented the idea that tongues were a private prayer language in order to fit his predicament! But his bad ideas were just beginning; he still had racism, murder and more bad teaching to come.
More on this vital topic in the future...