Plug-In Hybrid Vehicles
I have thought for quite some time that the medium term answer to the coming end of cheap oil is to begin to rely more on alternative fuels especially those from renewable sources such as ethanol and biodiesel.
The problem with these fuels is that they are limited resources. The amount of crops that can be grown limits the amount that can be created in a given year. It is unlikely to be possible to grow sufficient fuel source crops to supply the worlds demand at present consumption much less projected increases.
However, when combined with plug in hybrid electric technology these fuels could become a much more promising alterative. A small ultra-efficient diesel engine running on biodiesel could potentially boost commuter type vehicles to above 200 miles per gallon on an average annual basis while retaining the utility of the standard automobile.