There are so many people today who claim to be shamans making it more and more difficult to ensure the person you're working with is legit. The Foundation for Shamanic Studies, founded by Dr. Michael Harner, is a great resource, though I can't personally vouch for everyone in their listing. Lots of good information on this site and the only site I am listed (other than this space).
Shamanism is not a religion, but more a way of life, a spiritual way of looking at life. Wiki, in this case, gives a fairly good (but brief!) overview.
We all have a spirit. Throughout course of our lives that spirit can become damaged, fractured, or less vital than it could be. Shamanic healing comes in many forms and a good shamanic healer will be able to properly determine which healing modalities might best suit your needs and symptoms. To learn more about shamanic healing and what it might have to
offer you, you can check out this link.
This is a question I'm asked often. Whether there is a difference between being a shaman and practicing shamanism. And yes, there is an answer! Loren Torres gives the best answer to this question that I've found to date. You can read all about it here.
a Modern Practitioner for Today's World
THE Uncommon Shaman