Neo-shamanism is a shamanistic animist revival movement. It does not aim to copy or imitate any particular culture but uses aboriginal cultures as illustrative of a new kind of religion.
Plain old neo-shamanism is a disorganized and eclectic study. http://deoxy.org/ is a good example of a neo-shamanist website.
Core Shamanism is a specific branch of neo-shamanism founded by Michael Harner and based on ethnographic research. Harner believes he has found a common current across many different cultures, based on drumming and mentor-student relationships.