I heard about the case of Mr. and Mrs. H's supposedly haunted house on "This American Life" last Halloween, and meant to post it here. Upshot: feeling chilled, fatigued, and weirdly suffocated in some rooms of your house? Hearing and seeing strange things? Yeah, you might want to check for carbon monoxide before you go blaming ghosts. It can produce all those symptoms and more--"more" in some cases meaning "death."
Thought it was interesting, since not only should it make a lot of people rethink their ghost stories, but it might actually save some lives.
I still hope ghosts are real, sometimes, sort of. But a good scientist eliminates other explanations first.