(Idea taken from OscarWatch):

Don Cheadle
Movie: The Assassination of Richard Nixon
Performance: Traffic

Johnny Depp
Movie: Donnie Brasco
Performance: Pirates of the Caribbean: The Curse of the Black Pearl

Leonardo DiCaprio
Movie: William Shakespeare's Romeo and Juliet
Performance: The Aviator

Clint Eastwood
Movie: Unforgiven
Performance: Million Dollar Baby

Jamie Foxx
Movie: Collateral
Performance: Ray

Annette Bening
Movie: American Beauty
Performance: American Beauty

Catalina Sandino Moreno
Movie: haven't seen
Performance: haven't seen

Imelda Staunton
Movie: Shakespeare in Love
Performance: Vera Drake

Hilary Swank
Movie: Million Dollar Baby
Performance: Boys Don't Cry

Kate Winslet
Movie: Eternal Sunshine of the Spotless Mind
Performance: Eternal Sunshine of the Spotless Mind

Alan Alda
Movie: Flirting with Disaster
Performance: The Aviator

Thomas Haden Church
Movie: Sideways
Performance: Sideways

Morgan Freeman
Movie: Se7en
Performance: Driving Miss Daisy

Clive Owen
Movie: Closer
Performance: Closer

Cate Blanchett
Movie: The Lord of the Rings: The Fellowship of the Ring
Performance: The Talented Mr. Ripley

Laura Linney
Movie: The Truman Show
Performance: Kinsey

Virginia Madsen
Movie: Sideways
Performance: Sideways

Sophie Okonedo
Movie: Ace Ventura: When Nature Calls
Performance: Dirty Pretty Things

Natalie Portman
Movie: Leon (The Professional)
Performance: Closer