I just went downstairs to go to the bathroom. As I was walking back through the living room towards the front door to go upstairs, there was a creaking, like a door opening, and a banging noise. (It does not help that I was just watching an episode of Ghost Hunters.) I about had a heart attack before I realized that it was our storm door, which has neither operational catch nor hydraulic closer, blowing open in the breeze and banging on the little roof thingy that overhangs the front step.
It's funny to note that while my first thought was "Intruder!" my second thought was "I'm not wearing any pants!"