The Sneetches by Dr. Seuss. This is one of my absolute favorite stories. Focusing on prejudice, it demonstrates the silliness of segregating people based on categories (race, religion, gender, etc). The story's strength is that it shows just how arbitrary these categories are.
The Yellow Wallpaper by Charlotte Perkins Gilman. In this classic story, a new mother suffering from what we might today call 'post-partum depression,' sinks into a still-deeper depression invisible to her husband, who believes he knows what is best for her. Alone in the yellow-wallpapered nursery of a rented house, she descends into madness.
"Where shall I begin, please your Majesty?" He asked.
"Begin at the beginning," the King said, very gravely, "and go on till you come to the end: then stop."
"But I don't want to go among mad people," Alice remarked.
"Oh, you can't help that," said the Cat: "we're all mad here. I'm mad. You're mad."
"How do you know I'm mad?" said Alice.
"You must be," said the Cat, "or you wouldn't have come here."
(both quotes from Lewis Carroll's "Alice's Adventures in Wonderland," available in full-text here.)