I've been teaching with Moodle for two and a half years now and don't know what I used to do beforehand.
It is a very powerful suite of tools for teaching, and the advent of Moodle 2 (despite having some changes that through a bit of doubt and confusion into the Moodle community, at least initially) has lifted it another notch. It is compatible with a number of other major pedagogical tools such as SCORM.
It allows you to organise your units of work, present them in logical and attractive ways, embed multimedia, and keep tabs of student completion and marks. It also allows students and teachers to interact via forums and chat rooms, and for students to create their own bodies of information using tools such as the built-in wiki.
This is far more than simply a data repository (as I have seen some argue of Moodle). It is a fully fledged, fully featured teaching machine that is being taken up by increasing numbers of primary, secondary and tertiary teaching institutions across the globe. And not just because it's free.
Do yourself a favour and really check this out. Don't let the price full you. This baby sings!