While I don't consider myself a person who gets easily frightened, and while I also consider myself pretty skeptical of a lot of stuff on the internets, these two videos were definitely two of the creepiest things I have watched. I honestly contemplated turning the videos off while watching them.
Unbelievable Poltergeist Activity - Very Wierd
Truly terrifying poltergeist experience
More videos by this guy can be found here.