For a full listing of language codes as defined by ISO-639, see:

http://www.loc.gov/standards/iso639-2/langcodes.html

For a full listing of country codes as defined by ISO-3166, see:

http://www.iso.org/iso/country_codes

For details on RFC 3066, which established the localeID format, see:

http://www.ietf.org/rfc/rfc3066.txt