"The Perseus Project at Tufts University is the foremost Digital Library for the classical world, if not for the Humanities in general. In its collection of Greek and Roman materials, readers will find many of the canonical texts read today. The Greek collection approaches 8 million words and the Latin collection currently has 5.5 million. In addition, many English language dictionaries, other reference works, translations, and commentaries are included, so that anyone with an internet connection has access to the equivalent of a respectable College Classics library. The Perseus site is further enriched by intricate linking mechanisms among texts (resulting in more than 30 million links)."
It is a very good site for looking up references. http://perseus.uchicago.edu/