Back in college I wrote some plays. I remember what it was like to try and format a script. I never learned the "official" template (much to the annoyance of my directors). For those that take it seriously, however, there's word processors dedicated to the task. Celtx gets a link because the blogger who pointed it out not only speaks of it in Shakespearean terms ("Shakespeare says Celtx rocks") but actually shows a picture of a dude dressed up like Shakespeare :).