Below are some links to national organizations of various types in the U.S.A.
American Atheists
American Atheists, Inc., fights on the front lines of the battle for separation of religion and government, laboring for the civil liberties of atheists. Since 1963, American Atheists has challenged the intrusion of religion and religious tradition in schools, work, and public policy while educating millions about what it means to be an atheist.
American Ethical Union
The American Union is a national federation of Ethical Culture/Ethical Humanist Societies. Founded in 1876, Ethical Societies are congregational, religious humanist fellowships that meet regularly to explore ethical issues and ideals and to foster ethical relationships between individuals and groups. Ethical Societies are actively engaged in social justice activities such as civil and human rights and protecting the secular nature of government.
American Humanist Association
The American Humanist Association advocates for progressive values and equality for humanists, atheists, and freethinkers. Promoting the idea that you can be good without a god since 1941, and today headquartered in Washington, DC, the American Humanist Association litigates, lobbies, advertises, publishes, organizes and speaks out to promote the positive philosophy of humanism and further humanist causes. The Black Humanist Alliance, the Feminist Humanist Alliance, and the LGBTQ Humanist Alliance are all adjuncts of the AHA.
Atheist Alliance America
Atheist Alliance of America (AAA) is a non-profit umbrella organization in support of democratic local Affiliates to project a positive voice for atheism through community activism. Atheist Alliance for America is a national educational organization dedicated to developing and providing educational, advocacy, and community-building programs for the atheist community.
Black Atheists of America
Black Atheists of America (BAAm) is a non-profit organization dedicated to bridging the gap between atheism and the black community. Because religion is so deeply ingrained in the black community, black atheists often find themselves as a dual minority in the overall atheist community. BAAm hopes that its efforts will build a stronger overall atheist community by encouraging black atheists to be open about their stance on religion.
Black Nonbelievers
The mission of Black Nonbelievers is to provide secular fellowship, nurture and support nonbelievers in coming out, promote atheist pride, organize nonbelievers for charitable causes. They strive to connect with other Blacks (and their allies) who are living free of religion and irrational beliefs, and might otherwise be shunned by family and friends. Instead of accepting dogma, we seek to determine truth and morality through reason and evidence.
The Brights
Those who register into this Internet constituency have worldviews free of the supernatural deities, forces, and entities in which so many others believe. They stand for “a level playing field” that provides the same foothold in society as citizens who believe in the supernatural. The time is here to garner visibility and work for full social acceptance and civic participation.
Center for Inquiry
The mission of the Center for Inquiry is to foster a secular society based on science, reason, freedom of inquiry, and humanist values. The Center for Inquiry has centers nationwide as well as overseas. One of CFI’s programs is African Americans for Humanism.
Council for Secular Humanism
The mission of the Council for Secular Humanism is to advocate and defend a nonreligious lifestance rooted in science, naturalistic philosophy, and humanist ethics, and to serve and support adherents of that lifestance. Its activities range from magazine publishing and campaigning on ethical issues to holding conferences and supporting a network of autonomous local groups.
Deaf Freethinkers
This group was developed to nurture within the deaf community a broad understanding and respect for reason, science and the world around us.
Freedom From Religion Foundation
The Foundation works as an umbrella for those who are free from religion and are committed to the cherished principle of separation of state and church. The Foundation publishes the newspaper Freethought Today, broadcasts Freethought Radio, conducts annual national conventions, places freethought billboards and bus signs, sponsors student essay competitions with cash awards, promotes freedom from religion with educational materials, and is active in litigation to defend the separation of church and state.
FreethoughtAction
FreethoughtAction works to educate the general public about the personal, social and practical benefits of free and rational thought and action based on logic, reason and the scientific method as opposed to unquestioned acceptance of ancient tradition, religion and superstition.
Freethought Society
The goal of the Freethought Society is to raise awareness and acceptance of the non-theist community.
Hispanic American Freethinkers
Hispanic American Freethinkers (HAFree) is a non-profit national educational charity organization which serves as resource and support to all Hispanic freethinkers in promoting secularism.
Richard Dawkins Foundation for Reason and Science
The mission of the Richard Dawkins Foundation for Reason and Science is to support scientific education, critical thinking and evidence-based understanding of the natural world in the quest to overcome religious fundamentalism, superstition, intolerance and suffering.
Secular Coalition for America
The Secular Coalition for America is a 501(c)(4) advocacy organization whose purpose is to amplify the diverse and growing voice of the nontheistic community in the United States. They are located in Washington, D.C. for ready access to government, activist partners and the media. Their staff lobbies U.S. Congress on issues of special concern to our constituency.
Secular Woman
Secular Woman amplifies the voice, presence, and influence of non-religious women. Membership is open to all who support the mission.
Society for Humanistic Judaism
Embracing a human-centered philosophy that combines the celebration of Jewish culture and identity with an adherence to humanistic values and ideas, the Society for Humanistic Judaism offers a nontheistic alternative within Judaism. The Society organizes and supports inclusive congregations and communities, creates celebrations for Shabbat, Jewish holidays and life cycles, publishes resources and educational materials, and offers adult and children’s programs in communities and on campuses.
Unitarian Universalist Infidels
A home on the internet for positive atheists, humanists, agnostics, freethinkers, and others of like mind.
UU Humanists
The UU Humanists Association, strives to promote and extend the use of rational inquiry without supernatural considerations, followed by compassionate action in all human interactions. For over fifty years, UU Humanists Association and its precursor organizations have celebrated the Humanist Manifesto’s vision of a religion without gods through scholarship, teaching, promotion and advocacy – both within Unitarian Universalism and in the wider world.