American Model Yachting Association (AMYA): https://www.theamya.org/ Great information on a variety of R/C sailing yachts with many great links and useful information.
SeaWind COA web site: https://sites.google.com/site/seawindcoa/
Micro Magic Class Owners Association: https://sites.google.com/view/micromagic-us/home
DF95 COA: https://dragonflite95.us/
DF 95 boat and gear: https://radiosailing.net/
Lester Gilbert's website: http://www.onemetre.net/ An incredible amount of R/C sailing information from highly technical aspects to general overall discussions of sailing principles and tuning your boat for optimum performance.
Loyalhanna Dockyard: http://www.loyalhannadockyard.com/ Great site for sail and scale modeling needs.
Lots of information and videos aggregated by the Charleston Model Yacht Club: https://tinyurl.com/2p8njtpb
Scale Ship Modelers Association - North America: www.ssmana.org/
RC Gear: https://www.midwestmodelyachting.com/

RC Sailmakers
https://hotrcsails.com/
https://siriussails.com/