The first time I heard La Roux - In For The Kill (Skream Let's Get Ravey Remix) I really liked the female vocal over the top of a dubstep beat. I know Burial uses some female vocals in his stuff.
Some other tracks that do this that I know of:
Bat For Lashes - Pearls Dream (Skream's Pour Another Glass Of Champers Remix)
Florence & The Machine - You Got The Love (The xx Remix)
Fever Ray - When I Grow Old (Bassnectar Remix)
Rusko - Love Is Real
Deadmau5 & Kaskade - I Remember (Caspa Remix)
Little Boots - Meddle (Joker remix)
Adele - Cold Shoulder (Rusko Remix)
Kid Sister - Pro Nails (Rusko Remix)
Amanda Blank - Might Like You Better (Rusko Remix)
Would like to get more. Help me out dubstepheads.