In a previous post I discussed using Macros in Microsoft word as script formating aids. I am now using Celtx, which is excellent freeware script writing software.
It has an easy to use interface and once you teach students the basic structure of proper formating, they can quickly use the software. Best of all, it is an open source project. It continues to add new features that make it useful for more that just formating.
The website states:
Celtx is the world's first fully integrated solution for media pre-production and collaboration. It replaces old fashioned 'paper, pen & binder' media creation with a digital approach to writing and organizing that's more complete, simpler to work with, and easier to share.
The website has some tutorial videos that provide a great way to learn what it does. It is available for OSX, Windows, and Linux.
UPDATE: Version 1 is now out.