Green car geeks have known everything there is to know about regenerative braking ever since the first versions of the Honda Insight and Toyota Prius came out over a decade ago, but for most of the general public, it is still a mystery. That's why I think this video by Nissan does a good job; it's not about how things work on the technical level, but rather on the practical level.
The video tells the story of Neil Wagner, a man who just wants to see the sun rise from the top of a volcano (who wouldn't, right?). He happens to live on Maui, Hawaii's second-biggest island and a great place for electric cars since fuel is so expensive and you never drive too fast (it's an island, after all), so fulfilling that wish isn't too hard.
So Mr. Wagner drives up the volcano and gets his beautiful sunrise from above the clouds. And on the way down, we see how his LEAF electric car can harness the mountain to recharge its batteries, recuperating a good portion of the energy is expanded on the way up thanks to the fact that electric motors can also be used as electric generators.