"An Encyclopedia of Claims, Frauds, and Hoaxes of the Occult and Supernatural"

While the online version of skeptic James Randi's encylopedia is definitely intended to serve as a debunking resource, there's a lot of great background material in there for a writer, particularly his entries on the exploits of various fraudulent mediums (media?). For those not familiar with Randi - he isn't shy about his rationalist position, which some might find off-putting... He also has a quirky and snarky sense of humor:

bunyip In Australian aboriginal lore, a roaring, hairy monster known for jumping out of water holes to terrify passers-by. Also known as the yaa-loo and the wowee-wowee, names possibly derived from the reactions of a person encountering one at a quiet water-hole. It must be remembered that Australians tend to invent things (such things as the quite impossible duck-billed platypus) just to amuse themselves at the expense of gullible tourists.

There's lots of great stuff in it, skeptic or no - and like I said, plenty of good research material. [hat-tip to Will from MSNBC's "Clicked" column]