For those familiar with LMS's (Learning Management System) you'll know that all have their strengths and weaknesses. Many times I have found 'features' that I didn't appreciate and would like to have changed, yet the restictions on proprietary systems tend to disallow customizing of the system and interface. Enter the advantage of open source.
Moodle his a free, open-source LMS that has been in developement for several years now. It is based on other free software (PHP and MySQL), and as such doesn't paint the user into a corner with licensing issues. They are currently working on a release of version 1.7, and 1.8 is under development, and the functionality of the system is growing at a fantastic rate. And for those so inclined, access to the files means that editing the source, or even creating custom modules is a possibility, although this is not to be undergone by someone with limited knowledge of PHP.
The system as a whole is very stable, and the work that has gone into this project must have been enormous. From a teacher's perspective, using the system is quite self-explanatory. I will admit that some of the modules require quite a bit of digging to become familiar with, but if the time is put in, Moodle can be a very viable alternative to the services schools currently pay for. I have been working with it for a while now, and all things considered, I would definitely prefer Moodle over the proprietary systems I currently use/have used.
This is not a review, so I don't want to draw conclusions for you. Go to Moodle's website and look for yourself. Their website is actualy run under Moodle, which goes to show the versatility of the system. I would also recommend finding some demos of Moodle systems on the internet that you can take a look it. And if you think it is promising, talk to the IT department at your school about setting up a test server. Since it runs on both Windows and Linux it shouldn't be that difficult to convince them. ;)