Buddhism is a very old and expansive religion - there are many teachings and behavior prescriptions. It's also one of the few religions that doesn't give me the heeby geebies because the main tenents tend to be along the lines of being nice to everyone and leaving a small environmental footprint (in my limited exposure). The ultimate goal of every Buddhist is to become a Buddha.
In high school and college I was what a Sociologist would call a "seeker". I was looking for spiritual fulfillment and answers to questions like "What is the meaning of life", "What is my purpose in life", "How should I behave". I studied lots of different religions and religious teachings from the East and West, modern and tribal (although biased towards the modern Western religions due to my location in time and space): Christianity, Judaism, Islam, Mormonism, Buddhism, Jainism, Hinduism, Sikhism, Zoroastrianism, Bahái, Scientology, The People's Temple (Jonestown), The Manson Family, Heaven's Gate, Cargo Cults, early Mesopotamian religions, and more that I don't remember as well (wikipedia has a great list of religions).
My conclusions, looking back, are really simple. Perhaps if I had had some "spiritual" guidance when I was younger I would not have had to work so hard to come to such basic responses to religion. In short, here are a few summary conclusions on religions:
My spiritual quest was similar to that of a Buddhist. I read the scriptures and followed the paths to truth. I denounced untruth when I discovered it. Slowly I defined truths for myself, and came to understood how people came to believe untruths. I cast aside forever the ancient superstitions of my milieu. A learning Buddhist on the same journey might learn that all of who we are is defined by our physical brains. Modern science and neuroscience reinforce the idea that there is no soul. For example, after a brain injury somebody might change any number of mental/emotional attributes (for better or worse). I have been under anesthesia, and while under, I experienced absolutely nothing - as if I were dead.
Experience and the search for truth leads one to believe that there is no life after death - and if there is - it's probably not like the stories we've been told. Thus casting aside reincarnation, the Buddhist realizes that when he dies he will reach Nirvana because we all reach Nirvana. The human mind is still a relatively fragile organ, despite all its power. Not every human can cope with the thought of nothing after death. Only the mentally prepared and enlightened Buddhists realize they will reach Nirvana. The enlightened Buddhist does not want to take away the support from those who need it, perhaps he does not teach this part. The enlightened Buddhist teaches in order such that they the student can reach this conclusion on his own. Formerly a student, the Buddha sees that the answer was always there; he just had to look at it from a different perspective. These Buddhists become Buddhas, just like Atheists.
postscriptum: I don't mean all Atheists here. I just means the Atheists who are Atheists after a rational struggle for Truth. Also, I'm not suggesting that Atheists are enlighted Buddhists per se, just that the parallel between Buddhas and Atheists seems like more than a coincidence to me.