Moodle is a free and open source remote education system. The expansion can be transformed into a Modular-Object-Oriented-Dynamic-Learning-Environment, ie a Flexible Object Oriented Dynamic Learning Environment. The software works under MySQL and PostgreSQL database systems and in any environment that supports the PHP language (Linux, Windows, Mac OS X, etc.)
Moodle is an online course management system with features that can largely fulfill most of the activities that may be needed in a distance learning site. Moodle is easy to use by everyone (teacher, student).