This is a newer one: Canvas by Infrastructure
It is free and is looking to not only compete with Moodle, but the bigger systems as well, such as Blackboard. I have tried to get a demo up and running but it requires some proper configurations on this end. I have seen a demo though and read reviews. It seems great and easy to use.
If you are looking for options for LMS or CMS systems for your school. Check out this. Where I work, we have been running Moodle for quite some time and it is also great. I am not going to try to advertise any one product here, just giving an opinion. Just the look of Canvas is really clean and simple. Give it a look.