One effect that photographers have used for… well, since the beginning of photography, is long exposure images. Leave the shutter open for a while, and you get sharp images of static objects and a light blur of moving objects, in the same picture. But in motion pictures, this doesn't work because you have to capture enough images per second to create movement.
In the experimental film In Motion, Aaron Grimes simulates the effect of long exposure photography by blending individual video frames, one by one, in Photoshop. The result is a look at Tokyo in motion in a new way -at least a new way for video. Get more details about the technique at the vimeo page. -Thanks, Aaron!