Atheists:

Douglas Adams - wrote the Hitchhiker's Guide to the Galaxy series.
Woody Allen - Writer/director. 
Anaxagoras - old Greek philosopher, 1st person to put forth the idea of evolution around 600 BC.
Lance Armstrong - cancer beating, uber fundraiser for fighting cancer, 7 time Tour de Franch winner.
Isaac Asimov - science/science ficiton author, has a book for every classification of the Dewey Decimal System.

Dave Barry - American author.
Jeremy Bentham - British all around smart guy, came up with Utilitarianism.
Ingmar Bergman - director.
Ambrose Bierce - notable American author.
Marlon Brando - Academy Award winning actor.
Richard Branson - rich guy owner of Virgin enterprizes.
Leonid Brezhnev - Russian leader.
Warren Buffet - richer guy... 2nd richest man in the world, just donated $37 billion to fight AIDS and illiteracy.
George Gordon Lord Byron - British author/poet.

Albert Camus - French/Algerian Nobel Prize winning author.
George Carlin - comedian/actor/writer.
Andrew Carnegie - original rich benefector.
Adam Carolla - comedian, original of The Man Show.
Noam Chomsky - MIT linguist.
Arthur C. Clarke - sci-fi author of 2001: A Space Odyssey, et al.
George Clooney - actor.
Joseph Conrad - author of Heart of Darkness, Lord Jim, et al.
Auguste Comte - French philosopher, founder of sociology.
Francis Crick - DNA double helix biologist, won Nobel Prize. 
Alan Cumming - actor, Tony winner.
Marie Curie - chemist/physicist who won 2 Nobel Prizes.

Rodney Dangerfield - comedian/actor.
Richard Dawkins - really smart British biologist.
Denis Diderot - compiled the first rigorous encyclopedia.
Ani DiFranco - singer.
Paul Dirac - Nobel Prize winner in physics.

Richard Feynman - Nobel Prize winner in physics.
Larry Flynt - 1st Amendment rights advocate, magazine publisher.
Jodie Foster - Academy Award winner actress.
Sigmund Freud - psycologist.

Giuseppe Garibaldi - Italian revolutionary.
Janeane Garofolo - comedian/actress.
Mikhail Gorbachev - Russian leader.
Stephen Jay Gould - biologist/author.
Che Guevara - Latin American revolutionary.

Robert Heinlein - author.
Ernest Hemingway - Nobel Prize winning author.
Katharine Hepburn - 4 time Academy Award winning actress.

Billy Joel - singer.
Angelina Jolie - actress.
James Joyce - poet/author.

Alfred Kinsey - that sex study guy... go watch the movie Kinsey.

Vladimir Lenin - Russian leader.

John Malkovich - actor.
Marilyn Manson - singer.
Mao Zedong - Chinese leader.
Christopher Marlowe - author.
Karl Marx - political philosopher.
H. L. Menchen - author/journalist/social critic.
Arthur Miller - Pulitzer Prize winning playwright, married Marilyn Monroe.
Marilyn Monroe - actress, old school hottie.

Jawaharlal Nehru - Indian leader.
Michael Newdow - brought Pledge case to Supreme Court and is working on taking "In God We Trust" off our money.
Friedrich Nietzsche - philosopher.

Penn and Teller - magicians.

Ayn Rand - author of Atlas Shrugged and The Fountainhead, founded Objectivism.
Ron Reagan - president's son, stem-cell advocate.
Christopher Reeve - Superman, stem-cell usage advocate.
Nikolai Rimsky-Korsakov - Russian composer of Flight of the Bumble Bee.
Gene Roddenberry - created Star Trek series.
Salmon Rushdie - Booker Prize winning author of Midnight's Children and The Satanic Verses.
Bertrand Russell - British mathematician, won Nobel Prize for Literature.

Marquis de Sade - early erotic writer.
Carl Sagan - astronomer/physicist/writer of Contact, et al.
Camille Saint-Saens - French classical composer.
Margaret Sanger - early birthcontrol advocate.
Jean-Paul Sartre - French Nobel Prize winning author.
William Shatner - "We've.... got to.... try." Captain James Tiberius Kirk.
George Bernard Shaw - Irish playwright, winner of the Nobel Prize in Literature.
Percy Bysshe Shelley - British poet.
Burrhus Frederic Skinner - came up with Behaviorism.
George Soros - rich guy.
Josef Stalin - Russian leader.
Elizabeth Cady Stanton - worked with Susan B. Anthony for women's right to vote.   

Pat Tillman - left NFL to fight in army and was killed by 'friendly' fire.
Uma Thurman - actress who killed Bill.
Leon Trotsky - Russian revolutionary.
Ted Turner - owns the Braves, CNN, TBS, TCM, TNT, donated $1 billion to the United Nations Foundation, launched the Goodwill Games, and most importantly, created Captain Planet.

Kurt Vonnegut - American author.

James D. Watson - DNA double helix biologist, won Nobel Prize.
Steven Weinberg - Nobel Prize winner in physics.

 
Agnostics:

Margaret Atwood - author of The Handmaid's Tale.

Antonio Banderas - actor Zorro.
Lewis Black - comedian.

Helen Clark - Prime Minister of New Zealand.

Clarence Darrow - lawyer in the Scopes Trial, defending Scopes. 
Charles Darwin - did some science stuff and wrote some book.
Richard Dreyfuss - actor in Jaws and Mr. Holland's Opus.
Emile Durkheim - philosopher, wrote Suicide.

Umberto Eco - author of The Name of the Rose, et al.

Bill Gates - just donated over $30 to charity.
Matt Groening - Simpson's creator.

Larry King - CNN interviewer.

Bill Maher - comedian, has his own show.
Dave Matthews - singer/songwriter.

Bill Nye - the science guy... Bill, Bill, Bill, Bill.

Protagoras - 450 BC said the existance of god is unknowable.

Keanu Reeves - "woah"

Matt Stone - South Park creator.

Mark Twain - Tom Sawyer, Huckleberry Finn author.
James Taylor - singer/songwriter.