My as well christen this forum with someone i'm listening to at the moment.
Her voice ranges from soulful to operatic to just plain odd noises.
There are plenty of songs & videos on her myspace you can check out here..
MySpace.com - Diamanda Galas - Jazz / Blues / Classical - www.myspace.com/songsofexile
For further listening check out 'This Sporting Life' the album she did with Led Zep's John Paul Jones.