The World Factbook - Field Listing - Ethnic Groups - Provides a rank ordering, by country, of ethnic groups starting with the largest and normally includes the percent of total population. - https://www.cia.gov/library/publications/the-world-factbook/fields/2075.html
Ethnic group - Wikipedia - A general overview of what the term Ethnicity means. - http://en.wikipedia.org/wiki/Ethnic_group
Crossing Cultures - Contains personal stories of cultural experiences, essays, poems, artwork and photos. - http://www.digitrends.com/crossingcultures/
Ethnologue: Languages of the World - The Ethnologue is a catalogue of more than 6,700 languages spoken in 228 countries. The Ethnologue Name Index lists over 39,000 language, dialect, and alternate names. The Ethnologue Language Family Index organizes languages according to language families - http://www.ethnologue.com/