Moodle

From Moodle:

Moodle is a learning management system for producing Internet-based course web sites. It is written in PHP and is easy to install and use on Windows (as well as Mac OS X, Unix, Linux and Netware). It has been designed to support modern pedagogies based on social constructionist theory, and includes activity modules such as forums, chats, resources, journals, quizzes, surveys, choices, workshops glossaries, lessons and assignments. It has been translated into over 35 languages, with more on the way.

Moodle offers a free alternative to commercial courseware such as WebCT and Blackboard, and is being used by a growing number of universities, schools, and independent teachers for distance education or to supplement face-to-face teaching.