This online resource from UNESCO (which stands for United Nations Education, Scientific and Cultural Organization) allows you to search for information on endangered languages around the world.
For example, you can get a list of all the languages spoken by only a certain number of people globally—let’s say, between zero and 50. Or you could search for critically endangered languages in the United States, or for merely vulnerable languages in Australia. Or you could find out where in the world a particular endangered language is spoken.
An interactive map aids in the research. A fascinating resource!