For those that don't want to look it up, here is the ending in the movie:
Ma and Pa Joad in the truck, with Ma announcing that women see differently than men, that “it’s all one flow” for women, who see life as a “stream.” Like a stream, people too keep “goin’ on.” “We ain’t gonna die out.” “We’re the people that live. They ain’t gonna wipe us out. Why, we’re the people—we go on.”
But that wasn't supposed to be the ending. That was a commercial decision made by the Producer Zanuck who felt that the intended ending was too political. The director wanted to end with Tom's speech:
Then it don’ matter. Then I’ll be all aroun’ in the dark. I’ll be ever’where—wherever you look. Wherever they’s a fight so hungry people can eat, I‘ll be there. Wherever they’s a cop beatin’ up a guy, I’ll be there. If Casy knowed, why, I’ll be in the way guys yell when they’re mad an’—I’ll be in the way kids laugh when they’re hungry an’ they know supper’s ready. An’ when our folks eat the stuff they raise an’ live in the houses they build—why I’ll be there. See? God, I’m talkin’ like Casy."
But if you think the last part of the movie is striking, you should read the book. Spoiler alert, but there are boobs.
"For a minute Rose of Sharon sat still in the whispering barn. Then she hoisted her tired body up and drew the comfort around her. She moved slowly to the corner and stood looking down at the wasted face, into the wide, frightened eyes. Then slowly she lay down beside him. He shook his head slowly from side to side. Rose of Sharon loosened one side of the blanket and bared her breast. “You got to,” she said. She squirmed closer and pulled his head close. “There!” she said. “There.” Her hand moved behind his head and supported it. Her fingers moved gently in his hair. She looked up and across the barn, and her lips came together and smiled mysteriously."
