Considering that the 600-plus stories that make up Aesop's fables have been around for 2,500 years, you might not be surprised at the number of websites that come up if you google "Aesop's Fables." (You might be surprised at how many more come up if you google "detention hall.")
The Fables in Various Forms
Collections of fables on the internet are plentiful. You can start with a small searchable collection. More fables and and information can be found at aesopfables.com, the "hobby, fascination, and madness" of Rev. Gregory Carlson, SJ, priest, classic professor, and fable collector. At Aesopica.net Laura Gibbs, the translator for the Oxford World Classics, has a comprehensive site, with hundreds of fables, in multiple versions, including in Lating and Greek. You can also find contemporary versions, such as these visual retellings from students at the University of Massachusetts Amherst.
About Aesop and the History of the Fables
Not much is known with certainty about the life of Aesop, but you can learn about his life and times at Answers.com. You can also learn more about fables in general and their uses.