I find spirituality to be an exceptionally vague concept. It seems to describe, in a very rational way, a broad spectrum of not-particularly-rational experiences. Their lack of rationality seems to be a large part of what makes them spiritual; they entail an immediate, unquestioning apprehension of reality. That's about all that the ever popular experience of "oneness" amounts to, really: a turning off of the rational faculties without there being a loss of awareness.
Well, of course, I know what it is to have a credulous awareness of reality, and I'm very fond of having a credulous awareness of reality. A cobweb of rationales can be swept away by the tiniest gust of wind, whereas immediate reality, to the extent that it is immediate reality at all, insists on being what it is. I find that pleasant, because it allows me to turn beliefs into a little game; beliefs are like playthings to me.
I don't think that there's anything very spiritual about that, though. I'm an atheist, so you'd expect me to be raving about how glorious the universe is and how I get a sense of "God" from gazing upon it. But I think the universe is mostly a very dull place, and feel very little attachment to anything in it. All I really care about is the possibility of space aliens.
I think that what's spiritual about my lifestyle is the fact that I do things like roll the bad luck out of a die before it's time to put the die to serious use. Anyone who studies mathematical probability (which I don't, thankfully; I believe I'd die of boredom) would scoff at that practice, but it's something I believe in; it gives me a feeling that I'm directing some sort of intangible power. I feel that intangible power right in my chest, a sort of glowing warmth, and at the same time, I imagine a patch of peach-like colors. If that isn't spiritual, then I don't know what is. (On a side note, strange things are always happening with dice when I'm involved. I recently played Monopoly with someone, and neither of us could stop rolling doubles; he said it was first time he had ever seen anything like it.)