The number of "seculars" -- people who "say they are atheist or agnostic, or choose not to identify with a religious tradition" -- has risen from 8% in 1987 to 12% today. The proportion seems set to continue rising in the future, since the age group with the highest proportion of "seculars", at 19%, is people under 30, and "the number of seculars within each generational group is about the same in 2007 as it was 10 or 20 years before. Thus it appears that people have not become less secular as they have aged."
Self-identification is not the whole story, of course, as is shown by Europe and Russia where substantial numbers of people refer to themselves as "Christian" out of what I call "cultural inertia", while the majority of them actually hardly have any religious beliefs and do not engage in any religious rituals. That is clearly not the case in the US to anything like the same extent; according to the survey, 83% of Americans say they "never doubt the existence of God", 79% believe everyone will be judged by God for their sins, and 78% consider prayer an important part of daily life (note that the first two of these have declined slightly since 1987, consistent with the increase in secularism). However, the percentages agreeing with traditional religious views on homosexuality, the role of women, and concepts of good and evil, are all lower than one would expect from the figures above, and most have declined much more strongly than the relatively small rise in self-identified "seculars" would suggest. The one figure which seems jarringly discordant with the general trends is the high level of disapproval of internet pornography -- something which I attribute to the fact that internet pornography, like gay marriage, is a relatively new phenomenon and thus viewed with the suspicion that always tends to greet cultural innovation.
It is striking that, based on most of the graphs, religiosity in the US actually seems to have peaked in the late 1990s, with the decline happening since then. Thus, while the Bush administration is obviously strongly influenced by the Christian Right, it has not been able to spread or even maintain fundamentalist ideology in the population.