NPR has a series titled This I Believe, in which people from all walks of life share their essays on what beliefs they hold dear. I just ran across this one from November, in which Penn Jillette (of Penn & Teller fame) shares belief that there is no god. Regardless of your own view on the topic, this is an excellent read. My favorite bit, which I think sums up the whole essay is:
"Believing there's no God means I can't really be forgiven except by kindness and faulty memories. That's good; it makes me want to be more thoughtful. I have to try to treat people right the first time around."