Long exposure + action + flash can sometime equal interesting results! My flash is set to fire at the end of an exposure, rather than the beginning, so action is stopped at the end of the exposure, and motion blur follows, rather than precedes, the subject.
In the first photo, the unmoving background (including black boots and jeans on the right side of the picture) was burned in for the whole 1/8 second exposure, whereas the dog and ball just streaked by at the end. The motion was stopped by the flash, but since the dog and ball were only in the scene for a fraction of the exposure, the background comes through much stronger, and the dog appears ghostly. The second photo is just for fun.
Nikkor 18-105mm f/3.5-5.6
18mm (top) 24mm (bottom) - ISO 200
1/8s - f/3.8
Bounced off ceiling