What is Ruby you ask?
RGSS - Ruby Game Scripting System
Ruby is the name of the programming language used in RPG Maker XP! It's very flexible and allows easy editing within' the game structure itself. Sounds good an easy huh? NOT, if you've never had any programming experience before then it'll be quite hard at first. However don't worry because it's such a simple based system, it can be easily learned.
The path to learning Ruby!RGSS Tutorials on the main site:http://www.rpgrevolution.com/tutorial/rgss.php
Some External Links for Ruby, not RGSS:http://ruby-lang.org/http://rubyforge.org/http://www.rubycentral.com/
Feel free to post other helpful information regarding Ruby/RGSS and tutorials.