Hate to burst your bubble on the last statement, but that is not quite true. While the Prius has very low emissions at the talepipe and gets great gas mileage, one has to also look at how it is made.

The electric motor draws power from a nickel hydride battery, which comes from a large strip mine in Canada, then shipped on a diesel powered boat to Japan, where the Prius is actually built. Then the Priuii have to be shipped from Japan to America all of that involves a lot of carbon from boats. Lastly when the battery expires it has to be disposed of somewhere, and nickel hydride is a rather toxic substance.

The Prius does not make a lot of sense from a value perspective either. In terms of real world transactions. The Hyundai Accent for example is about six thousand dollars cheaper and gets nearly 40MPG. Factoring in the upfront costs, you would have to drive a Prius nearly a decade to make up for the difference with gas savings, plus if you own the Prius long enough the battery pack will have to be replaced, at an additional cost of 2000 dollars or so, not to mention the extra maintenance costs along the way for hybrid specific components.