Just read about this today... It's an application that claims to optimise your PC's performance by using a more efficient power save mode. Apparently, They say
If just 100 million of us optimize the efficiency of our computers’ energy consumption, we could prevent over 300 billion kg of CO2 gas emissions, equivalent to over 1.8 billion gallons of oil, in just the first year alone.Some more information about PC power consumption here.
What's interesting is that they provide a way to make the savings visible with this little widget so you can see the effects of your actions, thus reinforcing your behaviour.