Slide-casts.com just released a plug-in for Moodle 1.9. It allows you to convert your PowerPoints+audio files to slide-casts and view them in Moodle. If you don't want to share your slide-cast (most people don't), you can simply create what they call a "Learning Management System channel".
You can download the plug-in here: http://www.slide-casts.com/moodle/
(And yes, it's free)