I contend that we are both atheists. I just believe in one fewer god than you do. When you understand why you dismiss all the other possible gods, you will understand why I dismiss yours.

Stephen Henry Roberts, Historian, (1901-71)

Hurray for double-standards! When believers do good, they do good because of religion. But when believers commit evil, religion is being ‘used’.

Unknown

“Finally, I would like to assure my many Buddhist, Christian, Hindu, Jewish, and Muslim friends that I am sincerely happy that the religion which Chance has given you has contributed to your peace of mind… Perhaps it is better to be un-sane and happy, than sane and un-happy. But it is the best of all to be sane and happy. Whether our descendants can achieve that goal will be the greatest challenge of the future. Indeed, it may well decide whether we have any future.”

Arthur C. Clarke

“Because we must. Because we have the call. Because it is nobler to fight for rationality without winning than to give up in the face of continued defeats. Because whatever true progress humanity makes is through the rationality of the occasional individual and because any one individual we may win for the cause may do more for humanity than a hundred thousand who hug superstition to their breasts.”

Isaac Asimov, when asked why he fights religion with no hope for victory

The founding fathers of the United States, while not always atheist, had a very strong view on the dangers of religion, and felt strongly that religion had no place in politics and government; hence the constitutional separation of church and state. Here are some quotes. For a detailed list of quotes and views there is an excellent resource at monotheism.us.

As the government of the United States of America is not, in any sense, founded on the Christian Religion…

Treaty of Tripoli, 1796-97, Signed by President John Adams of the United States, after approval by the US Senate.

If you want the quote in context, you can read more about it.

Religious controversies are always productive of more acrimony and irreconcilable hatreds than those which spring from any other cause. I had hoped that liberal and enlightened thought would have reconciled the Christians so that their religious fights would not endanger the peace of Society.”

George Washington, Letter to Sir Edward Newenham, June 22, 1792 (my highlight)

I highlighted “their”, since this implies that George Washington did not consider himself a Christian.

Millions of innocent men, women and children, since the introduction of Christianity, have been burnt, tortured, fined and imprisoned; yet we have not advanced one inch towards uniformity.

Thomas Jefferson, Notes on Virginia, 1782

History, I believe, furnishes no example of a priest-ridden people maintaining a free civil government. This marks the lowest grade of ignorance of which their civil as well as religious leaders will always avail themselves for their own purposes.

Thomas Jefferson to Alexander von Humboldt, Dec. 6, 1813.

If we did a good act merely from love of God and a belief that it is pleasing to Him, whence arises the morality of the Atheist? …Their virtue, then, must have had some other foundation than the love of God.

Thomas Jefferson, Letter to Thomas Law, June 13, 1814

Feel free to read many more quotes and Jefferson's biography.

I've collected these from various sources, either other web sites or stumbled across them in articles/books or other places. One day I might make a fortune file out of all of them.

“Choose to live and choose to love; choose to rise above and give back what you yourself were given. Be moderate as you flee for survival in a boat that has no place for riches.”

Shin-eqi-unninni, ~1600 BCE, author of the most famous version of the Epic of Gilgamesh, from which the Bible's myth about Noah was plagiarized

“Hurt not others in ways that you yourself would find hurtful… For hatred does not cease by hatred at any time: hatred ceases by love – this is the eternal law… Be lamps [or islands] unto yourselves. Be a refuge unto yourselves. Do not turn to any external refuge… Owing to their creation of a Supreme Deity, men will become murderers, thieves, unchaste, liars, slanderers, abusive, babblers, covetous, malicious, and perverse in views. Thus, for those who fall back on the creation of a God as the essential reason, there is neither the desire to do, nor the effort to do, nor necessity to do this deed or abstain from that deed… ”

The Buddha, Siddhartha Gautama

“What you do not want done to yourself, do not do to others… Recompense injury with justice, and recompense kindness with kindness… When we see men of worth, we should think of equaling them; when we see men of a contrary character, we should turn inwards and examine ourselves… While you are not able to serve men, how can you serve spirits {of the dead}?… While you do not know life, how can you know about death?” Confucius

“I am not an Athenian or a Greek, but a citizen of the world… There is only one good, knowledge, and one evil, ignorance.” {Or maybe better: There is only one good, willingness to learn, and one evil, refusal.}

Socrates

“Have I done something for the general interest? Well then I have had my reward. Let this always be present to thy mind, and never stop doing such good.”

Marcus Aurelius, Emperor of Rome

“My country is the world, and to do good is my religion.”

Thomas Paine

“To have a positive religion is not necessary. To be in harmony with yourself and the universe is what counts, and this is possible without positive and specific formulation in words.”

Johann Wolfgang von Goethe

“Our civilization is not Christian. It does not come from the skies. It is not a result of 'inspiration'. It is the child of invention, of discovery, of applied knowledge – that is to say, of science. When man becomes great and grand enough to admit that all have equal rights; when thought is untrammeled; when worship shall consist in doing useful things; when religion means the discharge of obligations to our fellow-men, then, and not until then, will the world be civilized.”

Robert Ingersoll

“Is it a small thing to quench the flames of hell with the holy tears of pity – to unbind the martyr from the stake – break all the chains – put out the fires of civil war – stay the sword of the fanatic, and tear the bloody hands of the Church from the white throat of Science? Is it a small thing to make men truly free – to destroy the dogmas of ignorance, prejudice and power – the poisoned fables of superstition, and drive from the beautiful face of the earth the fiend of fear?”

Robert Ingersoll

“The philosophy of Atheism represents a concept of life without any metaphysical Beyond or Divine Regulator. It is the concept of an actual, real world with its liberating, expanding and beautifying possibilities, as against an unreal world, which, with its spirits, oracles, and mean contentment has kept humanity in helpless degradation.”

Emma Goldman

“My atheism, like that of Spinoza, is true piety towards the universe and denies only gods fashioned by men in their own image to be servants of their human interests.”

George Santayana

“The whole conception of God is a conception derived from the ancient Oriental despotisms. It is a conception unworthy of free men. When you hear people in church debasing themselves and saying that they are miserable sinners, and all the rest of it, it seems contemptible and not worthy of self-respecting human beings. We ought to stand up and look the world frankly in the face. We ought to make the best we can of the world, and if it is not so good as we wish, after all it will still be better than what these others have made of it in all these ages. A good world needs knowledge, kindliness, and courage; it does not need a regretful hankering after the past, or a fettering of the free intelligence by the words uttered long ago by ignorant men.”

Bertrand Russell

“This is my simple religion. There is no need for temples; no need for complicated philosophy. Our own brain, our own heart is our temple; the philosophy is kindness.”

The Dalai Lama