Ethnologue: Languages of the World.
The Ethnologue is a catalogue of more than 6,900 languages spoken in 228 countries. It tries to bring together the best information available on the languages of the world. Entries represent separate languages or probable languages (highly divergent "dialects") according to their best sources. Each entry lists number of speakers, alternate names, language family, where spoken, religion of speakers, etc. Search by virtually any variation of language name or dialect.