There is a myth going around--a rumor started who-knows-how-many centuries ago--that atheists are immoral. This is, in general, not true. Most of us are good, considerate citizens that only differ from religious folk on a few points. Just because we don't have to worry about going to Hell doesn't mean we don't have to worry about going to jail or stewing in our own guilt.
Hey, we're good people, I promise. We may not agree with everything a religious person thinks is wrong, but most 'bad' things are pretty damn obvious. Really, if it's only the fear of God that keeps you from raping, murdering and stealing, I would be worried.
The morals of an atheist are generally ride along with the norms of secular society at large. Even religious people have to adapt their values to their culture a bit at some point. Notice that while they crow about "traditional marriage," it is no longer legal or moral in this country to sell one's thirteen-year-old daughter to a sixty-five-year-old man for twelve camels and a fucking goat.
Some--admittedly extreme--Christians seem to believe that the secularization of society will lead to their own oppression (slippery-slope fallacy alert!). Others claim that God will punish us for this slow shift away from religion. To them, I have a few words:
The United States of America is still one of the (if not the) most religious countries in the developed world. I don't see any plagues of locusts, frogs, or anything else sweeping down upon our more secular friends and neighbors. In fact, it seems that the more religious the country, the more problems it has. Thus, if there is a God, it would look as if He's sending us a pretty powerful message.
On a related note: there are few things that could convince me of God's existence, but if a tornado was to drop out of a clear sky and somehow demolish the Westborough Baptist Church and nothing else around it, I may have to reconsider.