Moodle 2.2.2 - Produce/manage educational sites.. (Free): Moodle is a course management system (CMS) - a free, Open Source software package designed using sound pedagogical principles, to help educators create effective online learning communities.
You can download and use it on any computer you have handy (including webhosts), yet it can scale from a single-teacher site to a 50,000-student University. The Moodle website itself is created using Moodle, so check out the Moodle Demo Site or read the latest news at Moodle Buzz.