Freedom From Religion Foundation

The Freedom From Religion Foundation (FFRF) is an educational group promoting the constitutional principle of separation of state and church and educating the public on matters relating to nontheism. Incorporated in 1978, the Foundation is a national membership association of freethinkers: atheists, agnostics and skeptics of any pedigree. The Foundation acts on countless violations of separation of state and church on behalf of members and the public, including: prayers in public schools, payment of public funds for religious purposes, government funding of pervasively sectarian institutions, and the ongoing campaign against civil rights for women, gays and lesbians led by churches.

http://ffrf.org/