I received an email from Americans United for Separation of Church and State with the following banner image indicating how much money the following Christian Right organizations take in annually (click for larger version):

Most atheist organizations wouldn’t appear on this list. Only a couple would crack the very bottom of it.
We have a long way to go before politicians and society as a whole care about our concerns.
With less money, it’s harder to advertise what we’re fighting for. It’s harder to file lawsuits to defend our rights (right now, many groups have to pick and choose which important cases to take on).
With more money, there’s more awareness of the organization and exposure of what they represent.
With the end of the year approaching, I hope you consider donating to an atheist non-profit along with other secular charities.
Here’s a list of donation pages for various groups that could use your support:
American Atheists
American Humanist Association
Secular Coalition for America
Secular Student Alliance
Freedom From Religion Foundation
Center for Inquiry
Americans United