Check out the Center for Digital Storytelling http://www.storycenter.org/ They have a great "Cookbook" for how to approach this topic, available as a free download. They also run some fantastic workshops.
There is a nice sixteen minute video called Film School for Video Podcasters on the K12 Online Conference site. It was created by Matthew Needleman. Read through the entire page in addition to watching the video. He has some nice links.
Marco Torres has some great resources, too. He does amazing work with high school students. His wiki has some resources as well. I've been using iMovie with students on the Mac for about three year. It's really important to approve the scripts and storyboards in advance. I don't know what grade you teach, but sixth through eighth grade handle the software side really well. They need the guidance in the storyboarding, scripting, and planning aspects. They also love creating intro and outro music in Garageband.