Don't you hate it when you can't find something you know you have? I hate that, and I hate it even more to buy something that I know I already have.
However, after much crashing about the house and muttering, I found our UK to US electrical plug adapters:
Since I went to the effort to find them, I decided to do a brief bit of research, in case I (or someone else) wanted to buy them or ones like them. The specific plug pictured here is a Yung Li YL-6015. There are lots of companies that make adapters that will physically mate one nationality of plug to another. I find that they tend to be chintzy. However, these are very solidly made, and judging by the stamping on it, they conform to the electrical standards of both countries, including the in-plug fuse that's used in British wiring.
Oddly, I went searching for a place to buy those plugs, but I dont' seem to be able to find anywhere. The one place I could find at all was signalandpower.com, and they don't have an ordering page. I ordered these plugs in the spring of 2004, so I don't know where I went to order them; I do, though, seem to remember having to call someone. Signal and Power's contact page doesn't work, but they do have a phone number; maybe I just called them up and ordered them.
Disclaimer: These plugs, like most of their kind, only convert the plug style not the voltage! When in another country, only plug electrical devices into these plugs that are specifically rated for multiple voltages. My laptop power supply, for instance, says "INPUT 100-240V, ~1.0A, 50/60Hz". It will work fine on British 240V 50Hz AC power.
I will take the finding of these to be a good omen for my work day. Which means that I need to get to work. Excuse me, and have a nice day.