The following sites are large collections of other websites related to mythology. There are a lot of great links here!
These sites deal broadly with mythology in general, provide an overview of world mythologies, and/or include links to digitized primary sources
Websites focusing on myths and legends from various African nations
Myths and Legends of the Americas including Native American, Meso-American and Urban Legends
Links to websites covering mythologies in Asia including Indian, Japanses, and Chinese myths and legends
Many of the sites included here lead to some excellent resources on Mythology. And that's just the tip of the iceberg! But with so many online resources available it is extremely important to critically evaluate every source you use. The attachment below gives a nice checklist of things to consider when using a resource.
Websites examining the mythologies of Ancient Greece and Rome
Websites pertaining to Ancient Egyptian mythology
Links to sites dealing with European mythology including Medieval, Celtic, and Scandinavian myths