A few months ago I was given a Kill-A-Watt electricity usage meter as a gift. It’s a small device with a digital readout that you plug into a wall socket. When you plug whatever you want to test into the unit, it shows how many watts it’s drawing.
I’ve been measuring most of the items in my house and am recording my findings in a Google Spreadsheet. I’ve written up a page with my findings, which you can see here.