I don't give a fuck what anyone says or thinks, but Karen O of the Yeah, Yeah, Yeahs deserves a fucking spot on that list. Sexiest female vocalist around.
From Wiki:
Quote:
She was asked by Playboy to pose on their cover. She said on the subject, "If I see footage from our shows, I'm shocked by what I'm doing. But Playboy asked me about being on the cover. That's pretty insane. I may do it in the future."
Anyone who's good enough for the cover of Playboy is good enough for me. 
And I'd include Bonnie Raitt for fuck's sake...