Angelina Jolie is Dagny Taggart.
UPDATE: David Bernstein thinks Dagny should be played by 56-year-old Sigourney Weaver or 48-year-old Sharon Stone. Such appreciation of older actresses is admirable (if utterly divorced from the reality of Hollywood), but Dagny Taggart and John Galt are thirtysomethings during the novel. Why reduce the film's potential audience by casting older actors with a narrower appeal?
Regardless of his being a decade too senior, though, the only choice for d'Anconia is Antonio Banderas.