One of the most asked-about Bradbury stories is "All Summer in a Day". Barely a day goes by without someone posting to the Bradbury message boards enquiring about their vague memory of a short film they were once shown at school.
I was quite amused to discover this web page from the Chicago Tribune about "seasonal affective disorder," which refers to Bradbury's story. The page also has a direct link to the full text of the story.
As for the film, it occasionally appears on YouTube and elsewhere, no doubt without permission of the copyright holders. Its latest appearance is here.
In case you were wondering, the image on the left is the cover of the March 1954 issue of The Magazine of Fantasy & Science Fiction which contained the first appearance of "All Summer in a Day".