What do you want 'atheists' to offer exactly? It isn't a movement or an ideology. It's just a lack of belief in God and it is based on each individual's beliefs or lack of belief. There are numerous secular and atheist charity organisations and groups around the world. Such as UNICEF, Médecins Sans Frontières , Red Cross, etc.. Donations from such groups are not dependent on the receiver of said charities complying to any religious or non-religious ideology. Is that what you mean by offer?