LOTRO Plugin Compendium is an external program (available in Mac, PC, and Linux versions) for Lord of the Rings Online that takes all of the manual work out of installing plugins. In fact, it not only allows you install plugins, but it also allows you to update and uninstall them as well. It can be used quite easily to also discover new plugins that you might have not known of before!
I have been waiting a long time for someone to develop a program like this, which lowers the barrier to introducing people to plugins. The only down side that I can see to the program is that the author needs to approve each plugin manually, but he also does this to make sure that the plugin actually works with the program. So really it is hard to fault it too much for this fact. Regardless, I love this program and am thankful that it exists. This program is suitable for anyone; from those who want to dabble with plugins to those who use them all the time. This program is a must have.
Per Jason’s suggestion below I’m adding a link on how to use the in-game Plugin manager for those who may try plugins for the first time.