A corollary to atheism is materialism, in the philosophical sense. I don't believe there is anything supernatural in the universe. Although there are of course many things we don't understand, I don't think there is any reason in principle why we can not understand them.
In particular, I don't believe there is such a thing as a soul, or a mind separate from the body. Our selves and our consciousness are solely the result of chemical and physical reactions in our brains and bodies. Many people find it hard to conceive how this could be so. While I believe that it can be understood, I'm not going to tackle this complex topic here.
Life After Death
I don't believe that there is any such thing as literal life after death. I think it may have been Woody Allen who said "I believe in death after life—the other way doesn't make any sense."
The only true immortality we have is to be remembered after our deaths. We are remembered by our friends and children, and our influences live on through them, although they naturally dilute over time.
To be remembered in a more personal fashion is a form of immortality attained by only a few in the past, starting perhaps with Gilgamesh and the Yellow Emperor, or, rather, the real people behind the myths. It's interesting to think that, with the information explosion of today's world, many more people living today will be known in the future, if only as a photograph or a web page.
Without a belief in god, is it possible to have free will? If we are just matter without soul, then our actions boil down to just one molecule bumping into another.
Of course, we must first ask whether it is possible to have free will if there is a god. If we assume an omniscient god, then he (or she) can predict, and arguably even control, all our actions, so how do we have free will? Presumably only in some ineffable sense.
Anyhow, when it comes to free will, I am convinced by the arguments Daniel Dennett makes in his book Elbow Room. Free will really just means that we are able to do what we choose to do. And, for most of us, that is true regardless of our beliefs about the universe.
Since humans evolved from other forms of life, and since I believe that humans have no soul, it follows that there are great similarities between humans and other animals. In particular, I must consider ethical behavior toward non-human animals, and must ask whether non-human animals have any rights.
One of the basic ethical principles is that it is wrong to treat other people solely as means, rather than as ends in themselves. You must consider their needs and desires. To what degree does this apply to non-human animals?
I won't discuss this at length here, but I am a vegetarian and a supporter of the animal rights movement. For me, these beliefs are related to my belief in atheism.
Atheists Are a Minority
I live in the United States, where atheists are clearly a minority. As can be seen by the quote above from George H. W. Bush, who at the time was Vice President, there are people in power who are skeptical about the whole idea of atheism, even questioning whether atheists can be citizens. Fortunately, we are protected by the first amendment.
Even after all these years, it continues to be startling to me to see how deeply theism permeates U.S. society. God and prayer are invoked for all sorts of endeavors, both routine and extraordinary. I've seen crank arguments here and there that the U.S. is run by secular humanists; those people should try looking at it from the other side for a while.
Still, I have nothing to complain about. People in the U.S. are free to believe as they choose. Even the few who really object to atheists are relatively harmless, since atheism is invisible. Unless, of course, you start putting essays about it on the web.