@abge: Let me put it like this, in theory (rarely in practice) the religious person is supposed to act for the betterment of their particular God. This can be to the detriment of their own person (witness Mother Theresa, who arguably suffered physically in this world for her God...yeah, yeah, I know she did it for the emotional high, etc...i get it). On the other hand, an atheist, who is *not* driven to please some eternal, all-powerful being, will act for other motivations - the promotion of self, the promotion of humanity, the promotion of the Earth, etc. This thing, whatever it is that motivates them, in effect becomes their "god". Not that the Earth is giving them a directive, but I defy you to find a person, atheist or otherwise, who is not motivated to action by something they believe in and seek to improve. The wild-eyed atheist a capitalist pig works for his pocketbook, and will perhaps sacrifice certain pleasures others enjoy to to succeed in the pursuit he believes in. I trust you see my point. And, again, this in contrast to the religious person who (again, most often ONLY in theory and hardly ever in practice0 does all things with the motivation of pleasing his eternal, all-powerful God who will reward him in some way in the afterlife, the eternal bliss that lies beyond this world.
I am not trying to disparage either way of living (except to say most religious people are flat out hypocrites...but then most religious people are largely silent on their religion, too.) I'm just trying to examine these "opposites" rationally. (Opposites in quotes because they are both believers, but it is just more difficult to determine exactly what motivates and drives an atheist, and it is [supposed to be] easy to determine the driving motivation of the religious.)
Regarding "lack of belief' to being different from belief in nothing spiritual...I think you better check on the definition of atheist. If everyone on here is going to use their own person version of "atheist" then the entire discussion is pointless. I take atheist to be a person who believes in NO God, no unseen spiritual world, no life after death, no ghosts and angels...just existence as we see it and experience it, that our consciousness is a strange product of our physical brain, and involved nothing beyond the living tissue that we are made up of. As such, in my understanding of atheist, there is no possibility for "spirituality", karma or any of the crap. If you believe there is room for such things, then I would politely suggest you are agnostic - you think there is "something more", but you will not define it, and certainly will not define it as a conscious, interactive God.