Ever heard "On the Rim of the World" by Malvina Reynolds? It's the one that got me learning to yodel. A socially conscious yodeling song! Now, that's hard to beat.
I found it on Amazon.com on her "Ear to the Ground" CD, which I tried to link to here and created havoc in my posting. Anyway, you can get an MP3 of the song on Amazon, I think, for 99 cents.