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 (source: official website)
73% of 223 users have recommended it in sourceforge.net (http://sourceforge.net/projects/moodle/);
eLearning Blender website resview: http://joedeegan.blogspot.com/2010/03/scorm-problems-caused-by-moodle-re...
Ohlog.net review: http://www.ohloh.net/p/moodle