I just found a tool that fills a niche which I hadn't really considered to be available through Open Source Software. The niche is that of online learning site creation and the tool is called Moodle:
Moodle is an open source CMS (Course Management System), as Moodle describes itself. In other words; it's a web based interface to create web based training sites.
As far as features go; Moodle has everything that would be needed to create a complete web based training site, including quizzes, forums, multimedia, assignment submission/upload, LaTeX mathematics equation support, surveys, and student/user management.