Streak photography also works with long exposure, but instead gives off a 'smudging' effect. The cameras that are used for this technique have a slit built into them that limits the field of view to that exposed through the slit only. The image that is portrayed through the slit is then 'smeared' across the film. This usually ends up creating an image that doesn't resemble the original subject. The result are some very unusual photos:
Here, you can find a large catalogue of streak/slit-scan images by several different artists.
Finally, here is a really awesome example of moving slit-scan photography used on a webcam.