Greek Mythology Link is the best that I have seen; some parts of this site have been discussed below for quick reference but you really ought to look at the whole thing.
Specific Internet Sources
Search Engine: Search Greek Mythology. Sites are rated between 1-4 stars.
Bulfinch's Mythology is a standard work also organized by chapter. Organized in three volumes, volume one covers mostly Greece and volumes two and three cover King Arthur and Charlemagne respectively.
Mythology by Culture or Region covers the globe. Click on Egypt and you will get texts such as the Egyptian Book of the Dead.
Why Do People Need Mythology has several important links, among them a 300- page essay on morality, biology and ethics and another on the evolution of myths.
Myths and Legends is good for geographic distribution. Use the navigation bar on the left.Mythology. Arranged by topic and geography.
Timelines: Timeline of Greek History and Literature
Maps: Constellation Maps;
Texts: , The Internet Classics Archive, which covers 441 works in classical literature including mythology. You will also find many other texts in the Internet Sacred Text Archive , Folklore and Mythology Electronic Texts. and Perseus Digital Library
Bibliographies: Mythology References in Print
Oddities: CG Jung Page. I include this because mythology is so important in Jungian psychology. Recall that his theory of "archtypes" was rooted in mythology. And don't forget Joseph Campbell--here is his link: Joseph Campbell Foundation.