I, too, have had dealings with the Ouija although I didn't get into it like some of my friends. They got the bejeebers scared out of them on more than one occasion. I don't know if they are "demonic" spirits, but they do lie and at the very least they aren't "good" spirits IMO.
As for vampires, goodness I could write a book about that. Actually, I have considered doing just that. I've read about every non-fiction account I could find and there are some very interesting theories out there. First and foremost was that people didn't understand the process of decomposition or how illnesses spread, so when they dug up the first one to die from whatever illness they found the telltale signs of a vampire: blood at the lips, ruddy complexion, new fingernails and skin, etc. Along with the theory of Lupus being a real disease that could be mistaken for vampirism, there is also porphyria which is a blood disease. Porphyria makes one very sensitive to light, pale, sunken features, and since the blood is affected people with this disease often have a "craving" to consume blood (just as one might have a craving to eat dirt when lacking iron). Porphyria is very rare, though, and can't account for all the historical cases of vampirism.
The thing I find most intersting about vampire lore is that every ancient culture has a vampire-like being in their mythology. Some were hideous monsters like you see in Buffy and the campy films and books, others passed as humans like you see in the Anne Rice and Poppy Z. Bright books.
Can ya tell you hit on one of my pet topics?