There is a substantial literature on near-death experiences, including online articles and research.
Key books by scientific researchers are Kenneth Ring, Life At Death and Heading toward Omega; Michael Sabom, Light and Death and Recollections of Death; and Peter Fenwick and Elizabeth Fenwick, The Truth in the Light. Other books are listed below. See also this bibliography.
An influential study is by Pim van Lommel et al, Near-death experience in survivors of cardiac arrest: a prospective study in the Netherlands, which can be read in full here. See also Pim van Lommel, About the Continuity of Our Consciousness and a press report about the research.
Books by experiencers include Dannion Brinkley Saved by the Light, George G. Ritchie, Return from Tomorrow and Betty J. Eadie, Embraced By The Light.
A key sceptic text is Susan Blackmore, Dying to Live. This article by Dr. Jason J Braithwaite for the UK Skeptic magazine also argues against the survivalist interpretation of the ndear-death experience. For a critique of Blackmore's 'dying brain' hypothesis see this article by Greg Stone. See also Titus Rivas, Survivalist Interpretation of Recent Studies into the Near-Death Experience.
Anesthesiologist GM Woerlee is another sceptic - podcast and transcript of an interview here.
The International Association for Near Death Studies (IANDS) publishes news and articles on near-death research.
There is a useful chapter on near-death experiences in Edward Kelly et al, Irreducible Mind, which summarises the research and counters common sceptical objections
Michael Persinger claims to have demonstrated typical psychic experiences, including the sense of being outside the body, by activating a stimulus to the temporal lobe: The Paranormal: Mechanisms and Models
Some other books on near-death experiences, dying and related phenomena
Bruce Greyson and Charles P. Flynn (eds.), The Near-Death Experience: Problems,
Stanislav Grof and Joan Halifax, The Human Encounter With Death
R.E.L. Masters and Jean Houston, The Varieties of Psychedelic Experience
Andrew Newberg, Eugene D'Aquili, Vince Rause, Why God Won't Go Away: Brain Science and the Biology of Belief
Elizabeth Kubler-Ross, On Death and Dying
Raymond Moody, Life after Life
Kenneth Ring, Lessons from the Light: What We Can Learn from the Near-death Experience
Kenneth Ring and Sharon Cooper, Mindsight: Near-Death and Out-of-Body Experiences in the Blind
Penny Sartori, The Near-death Experiences of Hospitalized Intensive Care Patients: A Five-year Clinical Study. See my brief discussion at Paranormalia ('Just Coincidence', June 13, 2008)
See also a press release on Sam Parnia's ongoing research.
A wikipedia article has more references. This large website contains a number of first-person accounts, as well as useful supplementary information.
John Wren Lewis, a vocal atheist, dismissed all kinds of mystical leanings as 'neurosis' until he had a near-death experience as a result of food poisoning. The experience was devoid of imagery, which in others he continues to consider imaginary, but nevertheless was profoundly changed by it. He writes: I cannot and do not dismiss all those mutually contradictory accounts of meeting deceased relatives as mere delusion. For although my own experience included nothing like that, and left me very doubtful about any ordinary kind of personal immortality, the timeless depth of what I have come to call eternity-consciousness brings a sense of unity with all beings past and present every bit as real - indeed far more real - than the relationships which characterized life for me during my previous fifty-nine-odd years.'
Atheist philosopher Freddie Ayer describes his near-death experience here. SThis newspaper article reports on a conversation with a hospital doctor who claimed to have attended Ayers at the time, and that Ayers confided to him that he has 'seen a supernatural being' and would have to revise all his ideas.
This newspaper interview of novelist Fay Weldon discusses her near-death experience.