I like this series by Carl Van de Roer. It was featured on 20x200, which is one my my faves.
Here's a bit about the series:
The term "orb" is typically used to describe circular artifacts in photographs—artifacts which have been interpreted by some as spirits. Despite being debunked and explained (most commonly as backscatter from precipitation or dust), there's a surprisingly widespread belief that orb photographs document the supernatural. There are organizations, conferences, hunts, field experts, detectors and websites dedicated to spiritualist orb photography.
This photographic search for something larger than ourselves was the starting point for this project. I photographed people in landscapes that are partly obscured by precipitation. The subjects are seen searching for or interacting with orbs, which are represented as dots covering parts of the scene.
Read more here.