I'm sure we've all heard from at least one Christian that we've just replaced the Christian god with science. Or "atheists answer to nobody but themselves, and therefore they are their own god."
These people are falling into erroneous logic; they assume that everyone lives as they do. Not only that, but they assume that humans inherently construct their lives around a single entity--inherently. Note my word choice here, please. These are the same people who set out to disabuse native peoples of the tenets of polytheism, believing that the only way a person can live correctly is to worship only one god.
When you tell me that I am now worshipping science or myself, you assume that I am hardwired to focus my behavior, choices, and lifestyle around a central idea; having abandoned your god, I must therefore have replaced it with another single entity, and since I like science, it must be science. Alternatively, I might focus on my individuality; my god must be myself.
Sam Harris, in End of Faith, discusses the nature of belief, pointing out that every belief requires other beliefs as support. If you believe in the first commandment, you must also believe that it is impossible for humans to avoid setting up something as a god. This belief is erroneous, condescending, and egocentric.
It is quite possible to construct your life around a number of things, none of which rank above or below any of the others. In my opinion, this is the belief at the core of atheism; if you accept atheism as a possibility, you must also accept that humans do not need one all-encompassing influence over their lives.
Currently, my life is indeed constructed around many things, and in no particular order of effect or influence. Tomorrow it may change; tomorrow it may not. My life has no center, not even me; it is fluid and responds to its environment. Thus far, this has been the most freeing aspect of atheism for me.
I am the Lord your God; thou shalt have no other gods before me.
I don't need any gods at all--before, during, or after you. Thanks for the concern, but I'm good.