It begins with a Reddit thread, asking "What is the weirdest or creepiest thing you have found while hiking?" Some of these short-short tales are very effective.
Took my young children to a cave not far from the house. Popular spot, but we had the place to ourselves. You can walk through it in about 30 minutes without too much difficulty. It has a tiny exit at the opposite end. It was pretty muddy, so we decided to turn around and head back to the entrance. Halfway back, there was a lit candle sitting about eight feet up one side. It was definitely not there on the first trip. I went into full-on protective-dad-mode knowing there was likely someone hiding in the dark while we walked the rest of the way out.
That thread led to a much larger strand, a marvelous sequence of campfire spooky stories. The conceit is a search and rescue veteran sharing the creepiest experiences s/he has had or heard. Pore through these in a brightly lit, warm house, without stairs: 1, 2, 3, 4, 5, 6, 7, 8.
The author has now launched a Tumblr site.