Vjack at Atheist Revolution has a great idea. One that I am going to follow closely, and imitate.
Then What Do You Believe?
Christians often have many questions when encountering an atheist. Many reflect a lack of scientific knowledge (e.g., "Then how did we get here?"), a lack of moral development (e.g., "If there is no god, why should we be good?"), or just a lack of imagination (e.g., "Then what do you worship?"). However, there is at least one valid question to which more of us should be prepared to provide meaningful answers.
