Have you ever wondered how the professionals show motion in a photograph but also keep a portion of the image in focus?
Often they use a technique called panning. In panning you use a relatively slow shutter speed and match the speed of a moving object as it passes you by. In this situation you try to keep the object in focus and the background as a nice blur.
Here is how you do it:
Video by Canon
The result are images like these:
photo by danichro
See also: