Charging your mobile phone usually involves the use of a plug known as a "wall wart". These are not only unsightly when left plugged into the wall but they are constantly drawing electricity even when your mobile phone is not attached. Our friends over at Treehugger wrote about this a while ago and state a study claiming that only 5% of power drawn by cell phone chargers is used to actually charge the phone, the remaining 95% is simply wasted.
An easy solution is to unplug all your wall wart type plugs when not in use or place them on a power bar where you can switch them off with a single switch, but there may be times when it is not practical to unplug individual electronics such as a router or cable modem.
To deal with these device specific needs, some specialty power strips do exist. Two examples are the Wattstopper and the Smart Stip . Both solutions basically monitor specific outlets to sense whether an active device is plugged in. If no device is detected as being on and in need of electricity, power is switched off to those outlets.
Image via Treehugger.