There are all sorts of devices around the home that are drawing power when you might think they are off. Your TV for instance draws power when you hit the off button and your PC often does as well.
A company called Ventev has announced a new green charger called the EcoCHARGE that will eliminate the power drawn by mobile phone chargers even when the phone is not connected called vampire power. The charger can disconnect itself from the AC power when it sense no phone is connected.
The charger will ship in April for right under $30 in two versions. One version uses a mini USB connector and the other uses a micro USB connector. Both have a hidden full size USB port for charging devices like the iPhone.