Just to throw in another perspective/flavor from a rocker's point of view:
Skin from 'Skunk Anansie' rocks.
I have always been in love with Pat Benatar's voice.
I'm glad to see that 'Poe' got mentioned.
My newest 'discovery' is a woman named Julie Westlake. She sings in a hard rock band by the name of 'Hydrogyn'. She can rock with the best of them, and has a very melodic, powerful and sexy voice.
A pic of Julie: