Each day we cover the green sector of the automotive industry, and we see news coming from every direction touting some sort of new technology that is intended to reduce the effect our transportation has on the environment. Some of these technologies are easy to disregard as mere pipe-dreams, while others take a little more time to digest. For that reason, we've decided to take the opportunity on Earth Day to highlight some of the most promising green technologies that are either currently hitting the market or are just over the horizon. Follow along as we cover what we consider to be the top ten most promising green technologies. The ride starts here.