Kurtz was at the forefront of the modern skeptical movement. He founded the Center for Inquiry, the Council for Secular Humanism, CSICOP which later became the Committee for Skeptical Inquiry and Prometheus Books.
American Atheists first posted on their Facebook page of his passing.
American Humanists have a notice.
A nice summary by Hemant Mehta.
Ben Radford remembers at Center for Inquiry
Memories of Paul Kurtz | Center for Inquiry
Steven Novella writes In Memory of…