Harris Interactive gives these figures on atheists in America:
A plurality (42%) of all adults (but only 37% of men) thinks God is male, but only 1% thinks God is female. Almost half of all adults believe that God is neither male nor female (38%) or that God is both (11%).
If you add up the numbers, that works out to 92% responding on the gender of god. This suggests 8% who must not believe in any sort of god with any gender.
Barna has this to say:
85% of Americans self-identify as Christians. (2002)
7% of US adults classify as evangelicals (2004) (see Evangelical category for more information)
38% of US adults classify as born again, but not evangelical. (2004)
37% are self-described Christians but are neither evangelical nor born again
Atheists and agnostics comprise 12% of adults nationwide. (2004)
11% of the US population identify with a faith other than Christianity (2004)
This was down in the year before the Harris poll and has a higher percentage of atheists. Why? Did one survey have a lower quality? Did a whole bunch of atheists convert during the interval?
Some accurate figures about the number of atheists, agnostics, and general doubters of religion would be very helpful...