Some links.
The first is to a video which contains a little stretching but mostly people talking about how their dog is the most wonderful thing in the world.
Next is a long tedious looking wall of text about how dog athletes should focus more on flexibility and warming up/cooling down. It also provides some stretch exercises.
*On an unrelated note, this site plays an annoying sound whenever you mouse over certain buttons at the top, but it does have some cool graphics that play around the lights at the top.