CMB,
I'll second two of the opinions above, KorHaan's recommendation of the Canon IS binoculars, and Alexis's recommendation of the Swarovski 8x32 EL. I use the bigger Canon, the 10x42 IS L, and while it is too heavy to use one-handed for any extended lengths of time, the advantage of image-stabilization on what you can see, which is significant enough with two hands holding, becomes almost stupidly large if you need to use just one hand. Also, although the IPD does not lock in the Canons, the mechanism of it with a single-body and two twistable eyepiece assemblies is such that it really does not ever move on its own - at least it hasn't for me.
The Swaro 8x32 is an ergonomic delight, at least if you don't have very big hands and/or very narrow IPD. Like Alexis, I found it really easy and natural to hold, and while with the 42mm EL's I thought Swaro's marketing pitch on one-handed usability was pretty far-fetched, with the 32mm models it didn't feel like an exaggeration.
The Nikon 8x32 that Ed recommends is also very good, but does not fit the hand quite as well as the Swaro. Also, some units I have seen have had a pretty loose central hinge. The focus, on the other hand, is even smoother and easier for one-finger operation than the Swaro.
Kimmo