One idea that I've heard mentioned a few times is to use a percentage of the stored energy in electric cars to help power the grid overnight. The car owners would have to be compensated, but as battery technology improves (it has its own Moore's Law equivilant but the period of doubling is much longer), say, 20% of the energy stored in cars would end up being a very significant amount.
There is a problem with the idea though. Part of the reason why electric cars are attractive is that you can charge them overnight in such a way that it levels out the power demand, which makes power generation cost less. Not to mention many commute patterns mean that cars are not at home during the peak hours of electricity generation.
