|thanks vintageimages.org (PD)|
Let's not forget DogChannel.com's Dog College where you can do a short course with a quiz in many doggy subjects, from Dog Communication 101 to Canine Culture 401.
Would you like to try a class with a bit more commitment and rigor? MIT Open Courseware has People and Other Animals, a historical survey of human/animal interactions.
All these courses are free, and a fun way to stretch your mind toward different aspects of dog life!