It seems that most of us photographers are intrigued by the circles created by motion blur. I don't know exactly what it is about spinning subjects, but ... when blurred, they frequently make good compositions. Amusement parks, fairs and other events featuring rides are great locations to find circular motion.
Creating the blur simply requires a tripod and the exposure duration long enough to get the desired amount of blur effect. Since long exposures generally require low light levels, dawn and dusk (as seen in this example) are good times for this type of photography. Alternatively, use a neutral density filter
under brighter lighting conditions.