If you're writing a story or novel based on mythology--or one that includes invented mythology of your own--chances are you're doing a lot of research. While you always have the option of checking out dusty stacks of books from the public library, there's a whole host of websites devoted to this very topic that might be helpful.
Godchecker.com. This site is a repository of information on the god/goddess mythologies of over two dozen cultures. Some of the entries are a little sketchy, but I've yet to find a better overall view.
Godchecker also has fun stuff like a "Deity of the Day" and the "Holy Hit Parade" (ranking the most popular listings). There's also a place where you can buy mythic mousepads. You know, if that's your thing.
Scholastic's website has an extensive section of teacher-focused myth resources. My favorite is this myth writing workshop with author Jane Yolen, where she takes you through a few simple steps to create your own myth. It would be great fun as a writing prompt for kids, but it's just as good for writers starting the process of inventing their own mythology.
Timeless Myths is another great resource. Don't be fooled by the older website interface--this site has a wealth of information on Classical, Norse, Celtic, and Arthurian myths.
Do you have a favorite mythology resource, online or otherwise? Share it in the comments!