Here is a Google doc that Rosalind Anderson and the R&L Committee put together that lays out the performance expectations for the different referee grades.  The intro says:


In a perfect world, every beginning referee would take the field knowing every law and its proper application as well as understanding the difference between the perspective of a player and that of a match official.
In reality, referees begin with different knowledge and skill sets, and progression along the learning curve is varied. This creates challenges at the local level, between LROs wishing to assess and communicate referee ability and as referees strive to progress to higher level regional and national matches.
This workbook is a basic guide for the learning and assessment process. As such, it does not cover every law or situation, rather it focuses attention on skills in an order that facilitates even progress from basic to higher level processes and sets expectations for referees, referee coaches and teams about reasonable skills for referees at different levels.
This document is a beta version, meaning we will be adapting it as we learn from its application in the field. In addition, the document itself is "live" as we will add clips and resources as we find them as well as revisit it periodically to ensure it stays relevant to current World Rugby laws and directives.

From Advantage:

You can get the laws in an iPhone app or an Android app.

Haylee Slaughter sends along a color-codes toolbox of phrases and non-verbal actions she put together for refs to use in communicating with players during the match.

Brian Moore wrote on a refereeing forum a few years ago about managing the scrum.  He has a lot of opinions on the matter.  He also knows what he's talking about.  Somebody compiled the things he said into a post on RugbyRefs.com.  I've reprinted the text below.

Some of the information is a little dated because the laws have changed, but the principles remain the same.

Managing the Scrum – Tips by Brian Moore (ex England International Rugby Hooker)Moore represented England, winning a total of 64 England caps between 1987 and 1995, making him the 13th most-capped Englishman (as of July 2007). Moore played in three Rugby World Cups including in 1991 where along with Jason Leonard and Jeff Probyn he was part of a destructive English front row as they reached the final, losing a tight match 12-6 to Australia at Twickenham. Moore was also a member of the England side which won Grand Slams in 1991, 1992 and 1995. In 1991, he was voted Rugby World Player of the Year, a decade before the sport's governing body (the IRB), began its awards programme. He went on two British and Irish Lions tours, winning five test caps. In Australia in 1989, the Lions won the series 2-1, and Moore was famously caught celebrating the morning after on Sydney Harbour Bridge, doing aeroplane impressions. Having been a vocal critic of referees for many years. Moore took the Rugby Football Union’s Entry Level Referee Award course and qualified as a referee in 2010. (http://en.wikipedia.org/wiki/Brian_Moore_(rugby_union)) The following are tips by Brian Moore in managing the scrum, these tips were extracted from a rugby refereeing forum and was submitted by Brian under the alias/user BCM666. In this forum BCM666 (Brian) says “anything I post can be disseminated to anyone; including Paddy O'Brien!” so it is with this general exclaimer that the following document is produced.Pre-game brief about scrum

1. Before the game talk to the scrumhalf and the front row whilst the team is in the changing room. This is so that their peers know what they have been told and they cannot claim afterwards that you did not tell them something. It also helps you on the field because if they give away a number of penalties or free kicks it is highly likely that someone will say "He told you about this before the game - why don’t you listen"
2. I would tell them that whatever has happened previously in this game the ball is going to go in straight and by that I mean down the middle line which is below where the shoulders meet, not anywhere else. Furthermore, if this doesn't happen I will yellow card without hesitation.
3. To the front rows I would say that I will make a long mark where the engagement has to take place and they should use it because from the mark I will judging whether they or the
   

This is another intro thing.  Rugby Refereeing in Practice is a pamphlet the IRB (World Rugby before they changed their name and got a Marvel character logo) got from Australia and distributed for a bit as part of the Level 1 (which became Level 200 because of inflation) referee course.  It's one of the things I still send out before courses, but it's not part of the official USAR package.

  Turns out there are a lot more videos on the TRRA Youtube channel.  Some training videos on particular topics, some short clips of one call, and some match videos with Texas refs.  Check it out.

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 Bay of Plenty referee society has a page with an online course on introduction to refereeing rugby.  There is a downloadable workbook and a series of videos.  The modules are:
Contents:
Introduction and Welcome
Module 1: The Role of the Referee
Module 2: Fixture Organisation
Module 3: Whistle! Signals! Verbals!
Module 4: Where do I stand?
Module 5: The Kicks of Rugby
Module 6: Tackle Ball carrier brought to ground
Module 7: Ruck and Maul
Module 8: Scrum
Module 9: Lineout
Module 10: Offside and onside in general play
Module 11: Foul Play
Module 12: Advantage, free kicks and penalty kicks
Module 13: Assistant Referee/Touch Judging
Module 14: Method of scoring – ingot


I don't love their list of reasons for becoming a referee, listed below.  I'm pretty sure it's not a comprehensive list.  But the course looks pretty good for a beginning ref.

• Are You A Current Player Thinking Of Hanging Up The Boots?
  
• Or Maybe You've Suffered An Injury But Still Want To Stay Involved?
  
• Or Maybe You Weren't Very Good As A Player But Still Want To Contribute?