A nice overview from Joe Romm at Think Progress about the techniques that are being used to integrate wind and solar electricity into the energy grid despite the notorious variability of wind and solar.
Spoiler alert: it's going really well.
One of the key developments is the availability of highly accurate forecasts of wind and cloud cover that utilities are successfully using to forecast when they need to fire up a traditional power plant to cover a shortfall. Apparently it's the unpredictability of renewable sources that's the problem, rather than their variability. If utilities can predict their availability then they can cope with the variability.
But I have to say that I was amused by the idea of using the batteries of parked electric cars as a form of energy storage for the grid. The idea is that parked cars, at night, could supply energy from their batteries to the grid on the expectation that early morning wind will recharge these car batteries before the cars are needed for the morning commute. That seems far-fetched to me. But points for thinking outside the box.