Some good stats on digital direct's website about the wastage of standby buttons on electronic equipment.
Estimated annual CO2 emissions from devices left on standby:
Stereos - 1,600,000 tonnes
Videos - 960,000 tonnes
TVs - 480,000 tonnes
Consoles - 390,000 tonnes
DVD players - 100,000 tonnes
Set-top boxes - 60,000 tonnes
(Source: Energy Saving Trust)
Turn it off at the wall!