I noted that there are 165 people in the "Strong Atheist" discussion group. I bet, that there are some interesting things to describe.
I don't think that people have to have shouting matches wtih Fred Phelps, or bumper stickers that say "F*ck Religion", or write letters to the editor every week, to call youself "strong". Any involvement is more than most people will do.
For myself, I moderate 2 groups on A|N. I try to promote civil discourse when things seem to get out of hand. This, to promote unity even when there is strong disagreement. I do not discuss religion in the workplace, but when it is discussed, I don't hide my Atheism.
Even small actions add up. I'm wondering what others are doing now.