+ 1 for: Kate Bush, Neko Case, Annie Haslam, KD Lang & Joni Mitchell.
Here's a few who haven't been mentioned yet:
Karen Bergquist (Over The Rhine)
Dominique Durand (Ivy)
Jonette Napalitano (Concrete Blonde)
Kim Richey
Sharleen Spiteri (Texas)
Tracey Thorn (Everything But the Girl)