You gotta click on the exclamation mark in the logo on the Yahoo homepage... turn on your speakers:
http://www.yahoo.com

This isn't new – in fact, the yodel by Wylie Gustafson is from 1996! Yahoo back then paid him 590 bucks, German Spiegel reports, and has sinced used his voice in commercials and more. In 2002, Spiegel writes, Wylie sued Yahoo because he wasn't satisifed with his original payment, and Yahoo settled it out of court...

Ha ha..
Cooolll!!!

Thanks Philipp!

Has it always been on the exclamation mark? I would have thought it more widely documented.

It's been on the exclamation mark for as long as I've known about it!

And it's been mentioned here before :P
http://blogoscoped.com/archive/2006-08-18.html#n36