Lingualogue

The Ethnologue: Languages of the World is a web and print publication of SIL International (formerly known as the Summer Institute of Linguistics), a Christian linguistic service organization which studies lesser-known languages primarily to provide the speakers with native language biblical texts. It contains statistics for 6,809 languages (2000 edition) and gives the number of speakers, location, dialects, linguistic affiliations, availability of the Bible, etc. It is currently the most comprehensive existing language inventory, along with the Linguasphere Register (pay site, which is why I have the free Christian site listed primary).