From Advantage:

The TRRA does good webinars pretty frequently and posts them on their site.   A couple of them are unavailable when I click on them for some reason, but the content is available for most of them.

Topics include:

• Referee Development Through Self Assessment
  
• Tackling the Breakdown
  
• Setting the Scrum
  
• Assistant Refereeing
  
• Effective Communication
  
• Technical Zone & Assistant Refereeing
  

England rugby has a referee resources page with some online courses about the scrum and the tackle and about preparing for whatever their first referee course is. 

The USAR referees resources page also has a bunch of training videos like the one I posted yesterday on various topics.  At least some of them seem to also be available on Vimeo.  Let's see how many of them I can put on this post before Weebly complains.