My students and I investigated the allegedly best-documented case for a real NDE (i.e., one that really involved consciousness exiting the body, not just a vivid hallucination that did, which happens all the time). We published our findings in The Skeptical Inquirer a few years ago (Maria's Near-Death Experience, Various Authors, Vol. 20(Number 4)pages 27-33). In short, the evidence was VERY thin. There are several references in our article, especially those by Susan Blackmore, that are particularly good.