Crash was the shock winner at the 78th Academy Awards, winning best film ahead of favourite Brokeback Mountain.
Producer Cathy Schulman paid tribute to fellow nominees for creating "one of the most breathtaking and stunning maverick years in American cinema".
Ang Lee won best director for Brokeback Mountain but the film won only three of the eight awards it was nominated for.
Reese Witherspoon and Philip Seymour Hoffman shared lead acting honours for roles in Walk the Line and Capote.
Ang Lee, whose past films include Sense and Sensibility and Crouching Tiger, Hidden Dragon, saluted Brokeback's lead characters, Ennis and Jack.
Philip Seymour Hoffman
Best supporting actor
Best supporting actress
"They taught all of us so much, not just about the gay men and women whose love is denied by society but, just as importantly, about the greatness of love itself."
The cowboy romance had been described by bookmakers as the "hottest favourite ever to win best picture" after winning a slew of critics awards and the top prize at the Golden Globes.
But Crash, about racial tension in Los Angeles, enjoyed a late surge of support in a year dominated by intimate, thought-provoking films.
The multi-layered tale, featuring a large ensemble cast including Matt Dillon and Sandra Bullock, was co-written and directed by Paul Haggis - the writer behind last year's Oscar winner Million Dollar Baby.
Rachel Weisz (left) and Reese Witherspoon took actress awards
King Kong and Memoirs of a Geisha both won three awards in technical categories, equalling Brokeback Mountain's achievements, but this year's ceremony was not dominated by any one film.
Reese Witherspoon, 29, who won best actress for her role as Johnny Cash's wife June in biopic Walk the Line, thanked co-star Joaquin Phoenix.
"I feel so lucky to have gone on this journey with you," she said.
"People used to ask June how she was doing, and she would say, 'I'm just trying to matter'. I know what she means," added Witherspoon, who beat British rivals Keira Knightley and Dame Judi Dench.
Philip Seymour Hoffman, 38, said he was "overwhelmed" after winning best actor for his role as the acerbic author Truman Capote.
It was a good night for British talent, with UK film-makers winning three awards including best supporting actress for 34-year-old Rachel Weisz.
Weisz, who won the Oscar for her role in The Constant Gardener, called the award "a tremendous honour" and paid tribute to her "luminous" co-star Ralph Fiennes.
Box office hit Wallace and Gromit: The Curse of the Were-Rabbit won the best animated feature film prize, while Six Shooter picked up best live action short.
The animation Oscar is creator Nick Park's fourth Academy Award - but his first for a feature film.
"Someone once said if you make a bad film you make it alone, if you if you make a great film everyone made it with you," said animation partner Steve Box. "We made a great film, guys."
Park and Box said together: "Cracking cheese Gromit!"
Triple nominee George Clooney won best supporting actor for his role in oil drama Syriana.
Clooney proved a popular winner after a triumphant year that saw him nominated for three Academy Awards including best director and best original screenplay for Good Night, and Good Luck.
"We are a little bit out-of-touch in Hollywood," said the 44-year-old star. "I think that's probably a good thing.
"We are the ones who talked about Aids when it was only being whispered... We talked about civil rights... I'm proud to be part of this Academy, proud to be part of this community."
Cult satirist Jon Stewart, of The Daily Show, hosted the annual event for the first time, but steered away from controversy.
Instead, he poked fun at Hollywood's penchant for liberalism, touting the Oscar telecast as a rare "place where you can watch all your favourite stars without having to donate any money to the Democratic Party".