A trio of Oscar-winning actresses strut their stylish stuff on Hollywood's biggest nightNicole KidmanThe Oscar winner is no stranger to drama. Kidman—nominated again for Rabbit Hole, one of 2010’s rawest films—wore a strapless, embellished white Dior Haute Couture gown, topped off by a 19th-century riviere by Fred Leighton featuring 150 cts. of colorless diamonds. Where’s the drama, you ask? The opera-length necklace masqueraded as a choker in the front, but elegantly unraveled down her back, punctuating her outfit with an icy exclamation point of elegance.Opera-length riviere with 150 cts. t.w. diamonds, including graduated antique old-mine-cut diamonds; price on request; Fred Leighton, New York City; 212-288-1872; fredleighton.comUnder $70,00034-inch Lucia necklace with 32 cts. t.w. diamonds in 18k white gold; $64,000; A. Link, New York City; 800-342-5465; alinkandco.comUnder $