Starting with the story and breaking down the elements, building a schedule and sharing the reports, Celtx is an incredibly thorough tool for TV and video (or film, or theater). It's cross platform and totally free. One of the interesting features involves a built-in web browser, enabling some great collaboration opportunities. For instance, you can update multimedia assets (like photos) in realtime, so everyone has the same pic of the location for tomorrow's shoot. In fact, Celtx is built on Mozilla's Application Framework, and it's open source.