Tesla's Spirit Radio uses a simple crystal radio circuit connected to a computer sound-in jack to generate spooky sounds from all kinds of electromagnetic sources. As you will see, it creeped the hell out of Tesla himself.
"My first observations positively terrified me as there was present in them something mysterious, not to say supernatural, and I was alone in my laboratory at night." - Nikola Tesla 1901
"The sounds I am listening to every night at first appear to be human voices conversing back and forth in a language I cannot understand. I find it difficult to imagine that I am actually hearing real voices from people not of this planet. There must be a more simple explanation that has so far eluded me." - Nikola Tesla 1918
Is it science or the supernatural? Check out the video to see what the radio is capable of and, if your are so inclined, build one and decide for yourself. Needless to say, this would be a hit at a Halloween party. Hit the link for a complete set of instructions. [Instructables]