Moodle is a Course Management System (CMS), also known as a Learning Management System (LMS) or a Virtual Learning Environment (VLE). It is a Free web application that educators can use to create effective online learning sites.
Moodle.orgis a community site where Moodle is made and discussed.
Moodle Presentation[Version 2.1, HD] (0:02:47).

Why use Moodle?

Engaging Students - Videos
Teacher Version: What happens when you combine Google, Moodle, Wikis & Blogs?
Student Version: What happens when you combine Google, Moodle, Wikis & Blogs?