My stepdaughter loves Creepypasta, a website dedicated to publishing short stories designed to scare its readers. She trolls through that site and then can't get to sleep because it scares the hell out of her. There is one story in particular she loves, and she recently got me turned on to it -- "The Russian Sleep Experiment" about a Soviet sleep deprivation experiment that goes horribly wrong. The unidentified author created a macabre tale that's a perfect blend of horror, history, and medical facts and that drips with the frightening possibility that the events described could have happened. The audio version on IReadCreepyPasta.com makes the story even more spine chilling.
If you have thirteen minutes to be truly creeped out, then click here.