Norwegian dog trainer Turid Rugaas is a noted expert
on canine body language, notably calming signals which
are signals dogs give other dogs and humans that denote
stress. These are dogs attempt to defuse situations
that otherwise might result in fights or aggression.
Turid's site is http://www.canis.no/rugaas/index.php
The DVD shows footage of many calming signals, how dogs use
them, and how you can use them to calm your dog. This is the
DVD format and companion to the popular book, "On Talking Terms
with Dogs." Note - this is not a professionally filmed DVD rather
one done by dedicated amateur dog people; however, it does a
good job of illustrating the canine body language subjects it
addresses.
This short clip illustrates a few of the many calming signals.
I recommend that you either buy her book or video.