Seven Year Bitch: Nothing overly technical, but they rocked.
Ani Difranco: Great songwriter and live performer.
Tori Amos: I hear she's pretty good, but I've yet to aquire any of her albums.
Bonnie Rait: Queen of blues slide guitar.
Nina Gordon, and Lois Post: Both competant guitarists and not afraid of playing leads... anybody else remember Veruca Salt?

I think the big thing is that women tend to focus more on song writing and melody than showing off (more technical stuff).