18 "laws of UX": principles of user experience and how people interact with sites and online content. Some of this is visual design and visual communication; some is interaction design. I'm not sure that the Pareto principle is really a UX law, since it applies in many other situations, but you can stretch the definition a bit.
Introduction to usability testing. I've used this basic process (especially the "discount usability testing version"), or some adapted version of it, in several organizations. Mostly, I have used this with testing LMSs, but it works well for testing elearning too.