Aldi-Süd is selling a Strommessgerät (electricity monitor) this week. This is something that I have wanted for a while and for 9.90EUR, we invested.
When on and otherwise idle, my ThinkPad X40 consumes 25 Watts. Turning the LCD off, it uses just 18 Watts. Our DSL modem from Deutsche-Telekom requires 15 Watts. That is, it is using approximately as much power as the laptop when the screen is off.
The most interesting results are how much electricity devices use when they are connected but turned-off. My ThinkPad power-brick without the laptop connected uses 6 Watts. The 19" LCD uses 6-9 Watts. The biggest offender was our printer: when an HP OfficeJet 6510 is plugged in but off, it consumes 11 Watts. This is the same amount that it uses when it is on and idle.