The most credible source for information about NDEs is the website of the International Association for Near-Death Studies at iands.org. In particular, you might want to check under the Research tab for published papers outlining new findings from the most current research, particularly the two written by Dr. Peter Fenwick and Dr. Pim Van Lommel.
During the past 30 years, NDEs have been the focus of many scientific studies at universities and medical centers throughout the U.S. and around the world. Many medical professionals who have seriously studied the research and it is extensive no longer dismiss this phenomenon as hallucinations, intense dreams, or caused by physiological or pharmacological factors. The best analysis of the many physiological theories that attempt to explain NDEs -- as Hans Kung, who was referred to above, and others have tried to do -- is on a DVD that has a presentation by Dr. Bruce Greyson (from the University of Virginia Medical School) titled T3-Explanatory Models of NDEs. It can be obtained from the website above by clicking on the Conference tab and going to the 2006 conference that was held at the University of Texas M. D. Anderson Cancer Center in Houston, Texas.
There now have been many thousands of documented cases of near-death experiences: deeply mystical, often ineffable experiences the very essence of the religious experience. These accounts have a consistent internal structure and, cross-culturally, they reflect universal elements. That is, although no two experiences are identical, they all share at least some common elements. Just a few examples are that many experiencers have out-of body experiences (viewing their surroundings from above or outside their bodies while they are clinically dead or unconscious), meeting and communicating with mystical beings or deceased relatives, having a life review in the presence of "spiritual guides," etc.
Experiencers cut across all religious traditions including Christian, Jewish, Muslim, etc. Almost all report that their lives are dramatically changed after their experience, including often becoming more spiritual (almost always transforming atheists and frequently enhancing the spiritual perspectives of formerly religious people), trying to be more loving and caring, and often changing their work lives to the caring or teaching professions.
I am a member of the above association because I am interested in the topic. They keep you up-to-date with the latest NDE research along with e-mails of experiencer accounts every month.
Allen