But there is another group, much smaller and less-often heard from: unbelievers. In recent months, in books and on a sold-out off-Broadway stage, these religious skeptics have been raising their voices.
In the one-woman off-Broadway show Letting Go of God, for example, Julia Sweeney, the former Saturday Night Live star, tells the audience: "This Old Testament God makes the grizzliest test to people's loyalty. Like when he asks Abraham to murder his son Isaac -- as a kid we were taught to admire it. I caught my breath reading it.
"What kind of sadistic test of loyalty is that, to ask someone to kill his or her own child -- and isn't the proper answer, 'No'?"
She is just as hard on the New Testament.
"It was really hard to stay on Jesus' side when he started saying really aggressive, just hateful things," she said. "In Matthew he says, 'I come not to bring peace but a sword.'"
Equally harsh on religion is evolutionary biologist Richard Dawkins, whose book The God Delusion currently occupies the No. 1 spot on Publishers Weekly's bestseller list for religion titles. Dawkins argues that there is no evidence for a creator and is among the best known -- and surely also among the most strident -- of modern atheists.
"The God of the Old Testament is arguably the most unpleasant character in all fiction," Dawkins said at recent book signing in Washington. "A petty, unjust, unforgiving control freak. A vindictive, bloodthirsty ethnic cleanser. A misogynistic, homophobic, racist, malevolent bully."
He was a little kinder to the late Pope John Paul II.
"He suffered an assassination attempt in Rome and attributed his survival to the intervention of Our Lady of Fatima," Dawkins told the audience. "A maternal hand guided the bullet. One cannot help wondering why she didn't guide it to miss him altogether."
While much of the renewed militant atheism comes as a reaction to the strident rhetoric of the religious right, theologian Harvey Cox of the Harvard Divinity School said he thinks Dawkins is behaving just like those he criticizes.
"I think of Richard Dawkins as the kind of Jerry Falwell of the atheists," Cox told the PBS program Religion & Ethics NewsWeekly. "He takes the most narrow and the most legalistic side of religion and makes that religion -- and then he's against it."
"The usefulness of religion, the fact that it gives life meaning, that it makes people feel good, is not an argument for the truth of any religious doctrine," Harris said.
"Faith," he added in a recent speech, "is really the license that reasonable people give one another to keep believing when reasons fail."
Cox, however, thinks the scientists miss the point, arguing that unlike the material world, God is unprovable.
"It's when they step over and scientists say, 'There isn't any God because, look, we can't prove him.' Well, the canons of proof are not applicable to that question, and it's not something that can be proved or disproved."
The religious skeptics say that religion is not the only source for morality and ethics.
"If religion were the only durable foundation for morality, you would suspect atheists to be really badly behaved," Harris said. "You would go to a group like the National Academy of Sciences. These are the most elite scientists, 93 percent of whom reject the idea of God. You would expect these guys to be raping and killing and stealing with abandon."
Paul Kurtz, one of the nation's leading secular humanists and head of the Center for Inquiry, puts the emphasis differently.
"Secular humanists are defined not by what they are against -- we are not naysayers -- but what we are for. And we are for a humanistic world in which some of the basic human values and principles have an opportunity to be realized," he said.
The center has opened a Washington, D.C., office to counter what it sees as faith-driven public policy, especially the federal ban on funding embryonic stem cell research and the ongoing attacks on the teaching of evolution.
"We are concerned with the fundamentalist religion everywhere," Kurtz told a recent news conference in Washington, "and their alliance with political ideological movements to block science."
Cox said that, on balance, he welcomes the challenge from the current crop of atheists.
Atheism "always makes a comeback, I think, when religious people get too arrogant," he said. "When they begin to look as though or speak as though they know it all. When they begin to impose themselves in ways that are unwelcome to other people in society. Then atheism is kind of, for me, a welcomed critique of this arrogance."