I especially love the fact that there is a devoted wikipedia entry for this. It notes:

“In reality, cats do possess the ability to turn themselves right side up in mid-air if they should fall upside-down. The cat righting reflex is made possible in large part through being able to independently rotate the front and back sections of the body. This allows them to rotate without violating conservation of angular momentum by tucking in the front paws to lower the front section’s moment of inertia and extending the back paws to increase the back section’s moment of inertia. Thus, a cat can turn the front half of its body through a considerably larger angle than the back half.”