"Crash," featuring a huge cast in crisscrossing story lines over a chaotic 36-hour period in Los Angeles, rode a late surge of praise that lifted it past "Brokeback Mountain," a film that had won most other key Hollywood honors.
"We are humbled by the other nominees in this category. You have made this year one of the most breathtaking and stunning maverick years in American cinema," said "Crash" producer Cathy Schulman.
Lead-acting prizes went to Philip Seymour Hoffman as author Truman Capote in "Capote" and Reese Witherspoon as country singer June Carter in "Walk the Line," while corporate thrillers earned supporting-performer Oscars for George Clooney in "Syriana" and Rachel Weisz in "The Constant Gardener."
"Brokeback Mountain" filmmaker Ang Lee won best director for the tale of two old sheepherding pals who carry on a love affair they conceal from their families.
Lee, whose martial-arts epic "Crouching Tiger, Hidden Dragon" won the foreign-language Oscar five years ago, became the first Asian filmmaker to win Hollywood's main filmmaking honor.
"I wish I knew how to quit you," Lee told the audience crowd, reiterating the film's most-quoted line.
"Oh, my goodness. I never thought I'd be here in my whole life growing up in Tennessee," said Witherspoon, who, like co-star Joaquin Phoenix as Carter's soul mate, country legend Johnny Cash, handled her own singing in "Walk the Line."
"People used to ask June how she was doing, and she would say I'm just trying to matter. I know what she means," said Witherspoon, who told the audience the Oscar made her feel she was doing work that matters.
Hoffman's performance nimbly straddles the magnetic qualities of raconteur Capote and the effete, off-putting egoism of the gay author.
"Wow, I'm in a category with some great, great, great actors, fantastic actors, and I'm overwhelmed. Really overwhelmed," said Hoffman, who asked the Oscar audience to congratulate his mother for bringing up four children alone.
"We're at the party, mom," Hoffman said. "Be proud mom, because I'm proud of you."
Clooney's win capped a remarkable year, during which he made Oscar history by becoming the first person nominated for acting in one movie and directing another.
Along with performing in "Syriana," Clooney directed the Edward R. Murrow tale "Good Night, and Good Luck," which earned him directing and writing nominations and was among the best-picture contenders.
In "Syriana," Clooney effaced his glamour-boy looks behind the bearded, heavyset facade of a CIA patriot who grows jaded over U.S. oil policy in the Middle East.
"All right, so I'm not winning director," the first-time winner joked, adding that an Oscar always would be synonymous with his name from then on, including in his obituary. "Oscar winner George Clooney, sexiest man alive 1997, 'Batman,' died today in a freak accident."
Clooney also lauded Oscar voters for their daring.
"This group of people gave Hattie McDaniel an Oscar in 1939 when blacks were still sitting in the back of theaters," Clooney said, referring to the supporting-actress winner from "Gone With the Wind," the first black performer to receive an Oscar.
In "The Constant Gardener," adapted from John le Carre's novel, Weisz played a humanitarian-aid worker whose fearless efforts against questionable pharmaceutical practices makes her a target for government and corporate interests in Africa.
Weisz thanked co-star Ralph Fiennes and director Fernando Meirelles, "and of course, John le Carre, who wrote this unflinching, angry story. And he really paid tribute to the people who are willing to risk their own lives to fight injustice. They're greater men and women than I."
"Brokeback Mountain," which led contenders with eight nominations, lost in three acting categories (Heath Ledger, Michelle Williams and Jake Gyllenhaal) but picked up the Oscar for adapted screenplay by Larry McMurtry ("Lonesome Dove") and Diana Ossana and for Gustavo Santaolalla's musical score as well as for Lee as director.
The Oscar for original screenplay went to the ensemble drama "Crash," written by the film's director, Paul Haggis, and Bobby Moresco.
The raucous hip-hop tune "It's Hard Out Here for a Pimp" from "Hustle & Flow," whose expletive-laden lyrics had to be toned down for performance at the Oscars, won the prize for best song. The song was written by the rap group Three 6 Mafia, aka Jordan Houston, Cedric Coleman and Paul Beauregard.
Featuring dancers dressed as hookers and pimps gyrating on stage, the song's performance stood in sharp contrast to the other nominated tunes and the general stateliness of the Oscars.
"You know what? I think it just got a little easier out here for a pimp," joked Oscar host Jon Stewart.
The stop-motion family tale "Wallace & Gromit: The Curse of the Were-Rabbit" won the Oscar for best animated feature film.
Co-director Nick Park, who also made the hit stop-motion film "Chicken Run," thanked voice stars Helena Bonham Carter and Peter Sallis, who has done the voice of cheese-loving Brit Wallace for 23 years, since the filmmaker came up with the character in his student days.
"You've been an absolute gem, Peter, and you've sparkled all the way," Park said.
The Antarctic nature tale "March of the Penguins," a surprise smash at the box office, was honored as best documentary.
"King Kong," from "Lord of the Rings" creator Peter Jackson, won three Oscars, for visual effects, sound mixing and sound editing. The Japan drama "Memoirs of a Geisha" also earned three, for cinematography, costume design and art direction, while the fantasy epic "The Chronicles of Narnia: The Lion, the Witch and the Wardrobe" was picked for best makeup.
South Africa's drama "Tsotsi," based on Athol Fugard's novel about a young hoodlum reclaiming his own humanity, won for foreign-language film, beating the controversial Palestinian terrorism saga "Paradise Now."
Clooney was one of the marquee names among a lineup of acting nominees heavy on lesser-known performers. And with a best-picture field of lower-budgeted films that drew smaller audiences than the commercial flicks that often dominate the Oscars, the question was whether Hollywood's big awards night could lure TV viewers.
Oscar organizers hoped new host Stewart and the cultural buzz over front-runner "Brokeback Mountain" would beef up viewership.
Most of this year's nominees have turned a profit already, but there's not an 800-pound gorilla in the bunch, reports CBS News correspondent Jerry Bowen. That has some thinking that America won't care about a show that honors movies they haven't seen.
"Brokeback Mountain" is the most successful of the nominated films for best picture, taking in $75 million at the box office. But that ranks just 29th among all the films released last year. And "Capote," which has earned the least, ranks 104.
"Brokeback Mountain," though, has become a phenomenon far beyond those who have actually seen it, entering the pop-culture psyche with its tale of cowboys in love (acting nominees Heath Ledger and Jake Gyllenhaal).
Stewart used best-picture nominee "Capote" to set up a "Brokeback Mountain" wisecrack, saying the film "showed America not all gay people are virile cowboys. Some are actually effete New York intellectuals. It's true."