Kevin Drum writes and I quote in full because, since he's an Atheist all use is fair.

"JUST DON'T MARRY AN ATHEIST, OK?"....The final frontier:

From a telephone sampling of more than 2,000 households, university researchers found that Americans rate atheists below Muslims, recent immigrants, gays and lesbians and other minority groups in “sharing their vision of American society.” Atheists are also the minority group most Americans are least willing to allow their children to marry.

....“Atheists, who account for about 3 percent of the U.S. population, offer a glaring exception to the rule of increasing social tolerance over the last 30 years,” says Penny Edgell, associate sociology professor and the study’s lead researcher.

That 3% number is tricky, though. The real number seems to be in the range of 3-9%, and if you count "nonreligious" as the same thing it's more like 15%. What's more, if I had to guess, I'd bet the number is more like 20-25% if you include people who vaguely claim to believe in God but neither attend church nor do anything else that even remotely suggests they take their belief seriously.

As for trends toward increasing social tolerance, though, I'm not sure atheists really count as a "glaring exception." It's true that we generally can't get elected to high political office, but aside from that I suspect we don't suffer much serious social ostracism as long we don't insist on making obnoxious nuisances of ourselves. I never have, anyway, but maybe I've just been lucky. (And a Californian.)

UPDATE: Of course, it's true that making an obnoxious nuisance of yourself is generally considered a social faux pas no matter what you believe. On the other hand, it's also true that religious people seem to get away with it an awful lot more than us nonbelievers:

Robert Sherman: Surely you recognize the equal citizenship and patriotism of Americans who are atheists?

George H.W. Bush: No, I don't know that atheists should be considered as citizens, nor should they be considered patriots. This is one nation under God.

I don't think he ever apologized for that even after the election was over and the Christian Right had abandoned him.

Now I too am an atheist and I am neither surprised nor alarmed. The result is not new. In the USA, stated prejudice against atheists is vastly stronger than any other prejudice. Well I guess no pollster ever asked anything like "who do you disapprove of more atheists or child molesters," but if any did, I *don't* want to know about the responses.

Yet, like Drum, I never had the sense of any hostility at all. I admit, I had much less contact with red state American than Orange county dwelling Drum. I think the issue is that the rules of polite discussion of religion in the USA is that you only talk about religion with your co-religionists.

Christian activists are controversial because they break this rule, although IIRC leftist Christian activists are criticized for being leftists and accused of hypocrisy. I mean did anyone ever say that naming a political organization the Southern Christian Leadership Council offended against the first amendment ?

The norm that any controversial relgious opinion is kept to oneself is not toleration. To me it is neurosis. However, it does protect atheists by allowing us to stay in the closet. The only time I recall someone wishing to debate my atheism and convince me I was wrong with rational argument, that someone was a Dutch Catholic who lives in Italy. She is the very embodiment of John Stuart Mills' dictum that if you want people to take religious doctrine seriously you should have confessional diversity and open discussion.

Anyway back in the USA no such thing. Only proselytizing lunies who, for one thing, were incapable of rational argument and, for another, were bizarrely over polite (except for the bit about ringing on strangers door bells and stuff).

This means that it is very easy to be an in the closet atheist. In fact it is expected. I'm afraid it also means that it can be considered rude, intollerant and
"making an obnoxious nuisance of yourself" just to say "I am an atheist". I have no doubt that no God exists, that is, no hope that there is a God nor any fear that there is a God nor any such belief or sensation. Still, I suspect that people find it rude for me to say I am an atheist and expect me to be polite and declare, at least, an agnosticism which I do not experience.