If you've got something like a subwoofer that turns itself on - but you never use it without turning on your receiver (or stereo) consider a 'smart power strip'. These gadgets let you turn on / off a device based on power draw on a 'master' outlet. I've a couple of these. With the 'master' device off, my kill-a-watt (thing that measures power usage) shows zero. I'd expect it's using *something* but it seems very small.
I have a couple of warming devices (electric heated mat to stand on, radiant panel) under my desk (unheated basement office). I use a smart power strip to ensure the heating devices are off when the main monitor is off.

Also, as a side note, there's a thing called 'power factor' (essentially the time between volt-peaks and amp-peaks on an AC line). I don't think I've ever seen residential power that measures this BUT it does use energy. If you're building a PC, look for a power supply with power factor of 1 (same as resistive load). For AC units look for one with an inverter. You aren't billed for PF, so this won't save you money - but it will reduce the amount of energy the supplier has to push in at the other end of the grid, so if your goal is to lower the CO2 you're emitting...
FWIW, PF is a measure of inductive load (think big motors in a factory). If you're wondering about inductive cook tops / ranges, those aren'tn induction just an inductor connected across mains, but instead the mains power into DC then drives the coils under your pots at high frequency (tens or hundreds of kHz) through a resonant circuit - so they act like a resistive load.