Just like Graeme, I find this quote goes a long way to expressing my thoughts on religion:
Live a good life. If there are gods and they are just, then they will not care how devout you have been, but will welcome you based on the virtues you have lived by. If there are gods, but unjust, then you should not want to worship them. If there are no gods, then you will be gone, but will have lived a noble life that will live on in the memories of your loved ones.- Marcus Aurelius
Via: Exit, pursued by a bear.
I think you should live well not because a book decreed it with promises of posthumous reward, but because you believe living a good life is the right way to exist in this world.