A little while ago I tried to explain to someone that I was an atheist - by which I meant I wasn't just someone who didn't go to church but a non-believer by choice. This (elderly) lady had some difficulty in grasping the idea, so I was amused to see Ophelia Benson taking on the same problem at Butterflies and Wheels.
...Hey - I'm an atheist, and I tell you what, I not only don't believe in one god, I also don't believe in two gods, and three, and many, and many many. In fact, there are many one gods I don't believe in. In fact again, there is an infinite number of gods I don't believe in. Monotheistic, polytheistic, all-powerful deity, weak silly deity - I don't care, I'm impartial, I don't subscribe to any of them. I think that probably applies to most atheists. Probably pretty much all of them. In fact some wag (Bertrand Russell? Mencken? Twain? I don't know - some joker) pointed out that Christians are atheists about all gods except their own, and that atheists just add one more to the list.