(But, in short, the philosophy is: “100% efficiency in urban movement”.)

All the videos (except for two) are embedded from the Parkour series at ExpertVillage. As a side note: ExpertVillage shows ads before the video from time to time.

To start with, you may want to know the short history of parkour. Here is a movie from one of the parkour-evangelists:

Next, here’s a short sample of parkour from YouTube:

If you decide to try, you need to watch at least two more videos – about the equipment and safety measures.
First – equipment:

Safety should be self-understood, but in addition to that common-sense, here are some advices on how to behave while performing the most common parkour elements:

Next, there is a whole set of videos under the common title “training”. Here they are:

(I used to practice the one above at school… it was known as “goat jumping”)

And, of course, some video-hosting services like youtube will give you a variety of parkour-keyworded videos.