National organizations
- Freedom From Religion Foundation — Chapters in most US states. Legal advocacy for church-state separation.
- American Humanist Association — Local chapters and certified humanist celebrants nationwide.
- American Atheists — State directors and affiliate organizations across the US.
- Center for Inquiry — Community groups promoting science and secularism.
- Secular Coalition for America — State chapters advocating for secular government.
International
- Humanists International — Global umbrella for 170+ humanist organizations in 70+ countries.
- Humanists UK — Britain's leading humanist organization.
- Rationalist International — Network promoting rationalism worldwide.
Online communities
- r/atheism — 2M+ members discussing secular perspectives
- r/freethought — Curated freethought discussion
- r/humanism — Secular humanist community
- r/DebateReligion — Structured debate on religious claims
Find local groups
- Atheist Meetups — Local gatherings worldwide
- Humanist Meetups — Discussion groups and social events
- Skeptics Meetups — Science and skepticism groups
- Sunday Assembly — Secular congregations celebrating life ("church for people who don't do God")
For students
- Secular Student Alliance — Campus groups at 200+ universities
- Camp Quest — Summer camps for freethinking families