Interesting topic....
I've experienced feelings of being outside my body, within the dream state, as stuffwotifink said, it is a shockingly unmistakeable experience, it's almlost ridiculous how convincing it feels. The last time I experienced this was during a 10 day meditation session, in the afternoon when I was sleeping I had a vivid lucid dream and towards the end was outside of my body and then fell back in to me... WTF was that... meditation can induce these experienceS...
here is the delusional poppycock part though, about a year ago, I experienced these sensations for about a month, while wide awake on my travels... like IMPOSSIBLE, and I wouldn't dare tell anybody this..... people think you're a crackpot... but when this sort of experience hits you you're like WHAT THE FUCK IS THIS???? UTTER DISBELIEF..