It depends on who you ask. In fact, Beach Bum and I discussed this a while ago, referring to what I called "un-churches"; that is, humanist centers in places like California, where atheist families attend, as a counter to other Christian families going to church.
So basically a church for non-believers. Awww, people just wanna belong. Human beings are so pathetic. And what happens 50-100 yrs from now? Said Atheists then have a book that details the tenants of non-believing, and if you don't follow these state tenants, you are not a non believer and then must be ostracized? Sounds like a religion to me.
I firmly believe Humans have a "worship" complex. We worships Gods, cars, people, currency, bricks, houses, trees, frogs, birds, mountains, volcanoes, bodies of water, etc. If you think about it, it's quite stupid actually.