Hybrid Cars
This is a field that is maturing fast and it is very significant.
Fossil fuels (gasoline, petrol) are getting over. We need to find alternative sources of fuels. Until we find total replacements for the present fuel sources, we need to work on increasing the efficiency to help complete utilization of whatever is left of it.
Hybrid cars are a very good example of it.
Most fuel engines (pistons & cylinders) are tuned for high efficiency at average-speeds (say 40-60kmps - correct me if I am wrong, I am not an Automobile Engineer). So we tend to waste a lot of fuel when we start a car or are running it at low speeds in urban traffic.
An electrical engine(electromagnet & motors) on the other hand is efficient over a wider range of speeds, including the very low speeds. But we can not carry such heavy batteries in our cars to go just 100 km.
So what do we do? We combine both fuel engines and electrical engines. We use the electrical engine at low speeds, and fuel engine at higher speeds. So fuel is utilized most efficiently.
Aah, but where do we get the electricity from? Do we stil use batteries? No! We use regenerative braking. Everytime we break the car (which happens most in Urban traffic), instead of using friction to stop the car, we generate electricity (maybe using induction - again correct me if I am wrong). We store this electricity in a buffer fuel cell, and use it to drive the electrical motors at low speeds.
So we have effectively increased the milage by a large amount.
Read more about it at 
Or read the complete information at Howstuffworks "How Hybrid Cars Work"
And then there are organisations like NRDC which are asking people to break the chain - of dependance on fossil fuels. Read more about it here.
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