A very simple example, but I thought it looked cool enough to post.
The video shows the difference between consecutive frames in a video of me juggling. It has kind of an "edge detection" effect, but only moving stuff shows up. The second frame of the video shows the scene (since I start with an initial black frame).
Done with Processing.
This is first true video processing I've done. All other processing relied on only one frame, so they were basically just repeated photo-editing.