The right of Christians to prevent government from denying god's existence + the right of Atheists to prevent government from asserting any god exists + the right of everyone to argue publically for their beliefs = equal protection before the law.
Why I am an atheist Simple, straightforward, short explanation (14 questions and answers).
Divided Over God Dissenting opinion regarding the National Day of Prayer (NDOP) "America United Under God" campaign. Argues for government silence on matters of religious belief. Fits on single page, can be displayed wherever NODP posters are found (4 paragraphs).
Religion In America by Abraham H. Foxman, National Director of the Anti-Defamation League, December 7, 2005.
Some noteworthy historical documents on non-establishment On Liberty by John Stewart Mill 1869, A Memorial and Remonstrance June 20, 1875 To the Honorable the General Assembly of the Commonwealth of Virginia
The Freethought Zone A simple, brief, and good presentation of atheism. One criticism: They appear to be comparing 2005 statistics for the percentage of atheists with 1997 statistics for the number of atheists in prison.