http://www.nfatca.org A non-profit organization that represent the NFA trade and collector community. Their first priority was the creation of an NFA handbook which has been accomplished. Now they are turning their attention to other projects.
http://www.rmfcsa.org/ The Fifty Caliber Shooters Assn., Inc. (FCSA) was established in 1985 by a small group of dedicated people who set for themselves the mission to advance the sporting uses of the .50 BMG cartridge. The FCSA is a non-profit organization registered in Tennessee and Utah . The Rocky Mountain FCSA is the organizer of the Cheyenne Wells, CO and Ft. Morgan, CO gun shoot
http://www.smallarmsreview.com/ monthly publication that provides a forum for all aspects of the class 3 interests, as well as any aspect of the military small arms industry.