Literature: Folklore, Mythology & Fairy Tales
Aesop's Fables Online contains searchable and browsable versions of Aesop's Fables in various languages.
American Folklore contains "retellings of American folktales, Native American myths and legends, Tall Tales, weather folklore and ghost stories from each and every one of the 50 United States." Indexed by state, characters, region, ethnicity, tall tales, historical period.
Bullfinches Mythology: This online version is divided into the Age of Fable, or Stories of Gods and Heroes the Age of Chivalry, or Legends of King Arthur Legends of Charlemagne, or Romance of the Middle Ages.