This goes back to when I was a kid and would absolutely devour anything that smacked of the unknown and mysterious. Stories of people disappearing, just creepy stuff that was out in the world. I loved stories like that and still do today.
The internet has provided an explosion of these stories. A lot of it is fake, hoaxes if you will, but there is probably no better medium to surf late at night where it's just plausible enough to give you a good creep out.
So bring up which ones you think are the most effective. Black-eyed children? Slender man haunting your dreams?
This isn't really an example of what I'm talking about, but it pretty well encapsulates the sort of thing I'm looking for.
What sort of stuff have you found while surfing the net that has really creeped you out?