Here in the halls of Language Weaver, we received unexpected news about the world's supply of languages. As you know, extinction of minority languages is rapidly reducing the number of languages in the world. But the latest edition of Ethnologue lists 83 new languages from 19 countries, according to an article by Michael Erard in the April 17 Science magazine. Naturally the languages aren't new to those who speak them, but they are new to linguistic research and classification. Most of the languages are spoken by minority groups in remote areas, where linguistic fieldwork has been inhibited by geography (such as roadless mountain terrain), social conditions (such as war or ethnic repression), or government regulations.
Erard's article focuses on the 2006 field work of researcher Jamin Pelkey, who gathered linguistic data in the Yunnan province of southwestern China, bordering on Laos, Vietnam, and Myanmar. Chinese tradition lumps everyone in the area into an ethnic group called Yi, who were assumed to speak a single unified language. But Pelkey has found 24 mutually unintelligible languages so far. Other researchers speculate that there may be as many as 150 distinct languages to be found in the area, and field work is ongoing. Linguists anticipate finding hundreds more languages elsewhere in China, Myanmar, the Amazon, and other less-traveled regions. Look for the article at http://www.sciencemag.org/cgi/reprint/324/5925/332a.pdf or on the author's website http://www.michaelerard.com in June.
Incidentally, the current Ethnologue lists a total of 6909 living languages, an increase over the vague "about 6000" we used to teach in beginning Linguistics classes. More precise knowledge is available now due to the increased interest in linguistic field work, which has multiplied the funding opportunities and the supply of willing students to do the research.
Our March 2009 article on endangered languages neglected to mention an additional resource for learning about them. Ethnologue, the definitive online language survey maintained by the Summer Institute of Linguistics, provides a portal on endangered languages at http://www.ethnologue.com/nearly_extinct.asp