Spiff, how could you of all people not mention Susannah Hoffs?
Metal and 'ard rawk wise, how about Doro, Kimberly Goss and Melissa Auf De Maur?
Or if you're after something a tad mellower, Patti Smith, Kate Bush, Suzanne Vega and Tori Amos.
I also really like Michelle Branch for some reason, though I haven't quite worked up the nerve to buy one of her albums yet. If I did, it would most likely be Hotel Paper.
W