The Out Campaign is an effort started by the Richard Dawkins Foundation to get atheists to publicly declare their status. It suggests to display a letter "A" in Zapfino font and scarlet color as a symbol, not of our disbelief, but of our willingness to declare something that by now should be obvious: the world is not for, or made of, believers only.
I have been pretty much undecided about what to do as an atheist. On one hand, I think it's very important to voice our disbelief, as otherwise, those in power will only respond to the interests of the superstitious majority. On the other hand, I see religion dying a natural death and I don't want to give religious leaders more reasons to fight.
My decision so far is on the side of speaking up. I think atheists need to have a saying, but not to try to convince the more credulous people that their pixie in the sky does not exist. What we have to do is to give a hand to that large group of people who were raised to belief in something following a cultural custom, but that now that they are not children, cannot reconcile the teachings of religion with their own life and reason.
See also: Pharyngula
