Hughes Research in Somerset has built a ramp that uses the traffic that passes over it to create electricity. It can be used to power traffic and street lights.
There's a video about it here.
This is a great time for inventors. The need for alternative sources of power is going to be so great that whole new sectors of the economy will be created to provide for it. There won't be just one or two sources of energy, but tens of them and they'll come in all sizes. The benefits will be environmental (low emmissions, etc), political (no dependency on dodgy regimes) and economic (new markets rewarding new ideas).