How many times have you been in a situation that you can't put both hands on your camera to get the picture you want? This happens to me a lot! For example, driving through a scenic area, you stick you camera out the window to (hopefully) get a great shot. Or, you are in a crowd and you need to get a high vantage point. Or you are holding something precious in one arm, and you only have one hand free.
This is your opportunity to show off your best one-handed shots. You have to have used only one hand to snap the picture, and you have to justify, in the description of your image, why you only used one hand. A bonus is given (hopefully) to the picture that really conveys one-handedness on the part of the photographer.
I intend for this to be an attractive challenge for someone without expensive equipment. Are you really going to hang your Canon D1 out the window of a car going 80 MPH? I sure hope not! But your $150 PowerShot is OK for this.