the Mongolian or Tuvan throat singing mentioned above
is very interesting. http://khoomei.com/

The fellow at the website here (Steve Sklar)
teaches it and has a band (BigSky) that performs in that style.

it seems that people who herd critters (swiss cows, tuvan yaks, etc)
have perfected this method of singing.

these folks are most famous for this style
http://www.huunhuurtu.com/
there are some Buddhist monks who
do this also, but rumour has it that they
learned it from the Tuvans.
but this is not exactly yodeling,
so i should start another thread....