They could also be sleep paralysis. I've experienced that frequently and it resembles being out of the body- there is a scary/trippy feeling to it...I couldn't move my body, but my "self" moved beyond my body, and seemed to hover,float around, move through walls, etc. Pretty weird stuff. I could feel an episode coming on like a creeping paralysis. It always happened while lying on my back, just as I would lie down for a nap; studies have actually found that correlation- so I switched to sleeping on my side, and no more out-of-body traveling! That may be different from astral projection but it sounds very similar to me.
Another time I've had that sort of sense (other than from hallucinogenic drugs of course) was from meditating once. I'd been meditating daily for weeks before I had the experience of lightness and feeling beyond earthly self. I wish I had the discipline to sit still and do that more, but I am SO figety! It was a beautiful experience.
I also felt a soaring of the spirit once while chanting with 50 women in a Buddhist temple in Tokyo. The voices merged into a sound, harmony of the spheres, and that was definately an elevation beyond the material.
Altered states are very interesting aren't they:stoned: