Graphic warning: This otherwise excellent article, unfortunately, has a nude picture on its third and most important page.
The Secret History of the Triple Goddess, Part 1: Triads, Triplicities, and Trinities
The Secret History of the Triple Goddess, Part 2: The Search for the Triple Goddess of Antiquity
The Secret History of the Triple Goddess, Part 3: Will the real Triple Goddess please stand up?
13 Things You Don’t Need to Know About the Triple Goddess (but are kind of interesting)