Somehow world music (for want of a better term) seems to lend itself to groups (or bands, which may not be the same thing). Just in Australia, there's Blindmans Holiday, Xenos, Vardos, Doch, Transylvaniacs, the Kazakhstan Cowgirls and lots of klezmer bands - Klezmania, Klezmeritis, KaOz Klezmer, Counterfeit Gypsies.

For folk harmonies, no one beats The Fagans, although you don't get to hear them too often.