Slow shutter-speed can be good for many things (Eg panning, sports and low light photography). But if you, for a moment, stop trying to create the conventional photograph with pin-sharp points of focus, and start playing around with slow shutter-speeds you can get some wacky results.
To create photos like this example set your camera to a slow shutter-speed and experiment with moving the camera during the exposure. You must use a long exposure to ensure you have long enough to move the camera and fit the whole scene that you want to capture in. If you end up with almost white images as results, change your film speed to compensate for the slow exposure.
If the exposure is still going after you have panned the scene, try panning back the other way. You can also experiment with moving the camera up and down, in a bouncing motion from left to right. There are many possibilities. Just take your camera out and have a go! This can be tried in daylight or at night with street lighting.