A UK based company, Riversimple, introduced the hydrogen fueled "Urban Car'. The full story is at http://edition.cnn.com/2009/TECH/science/06/16/riversimple.hydrogen.car/index.html
They claim 30 grams of CO2 per kilometer and a H2 cost of about 25 US cents per mile for fuel.
Excerpts for the article follow:
'The Urban Car's power comes from hydrogen fuel cells which are linked to four electric motors situated over each of the car's wheels. Almost all of the braking is done by the electric motors, which then capture the energy of the car in motion and store it in a bank of ultracapacitors. In conventional cars, the energy generated through braking is lost as heat.'
'The energy stored in the Urban Car's electric motors is enough to power 80 percent of the car's acceleration. That reduces the energy demands on the hydrogen fuel cell, meaning it can be one fifth of the size of one used in a normal car. The lighter fuel cell also makes it more energy efficient.'