What is the best screenwriting software?
Internet Filmmakers' FAQ
area of screenwriting software this is even more relevant, as most screenwriting applications are simply glorified text editors, designed to save you time by providing short-cuts for text formatting.
In the area of commercial applications, the two market-leading products are Final Draft and Movie Magic Screenwriter. Both applications are available on the Windows and Mac platforms, and retail for around USD $200 - $250. A downloadable, time-limited demo of Final Draft is available from the Final Draft web site. Unfortunately there isn't a demo of Movie Magic Screenwriter, although it is the official screenwriting software of the Writers' Guild of America and Project Greenlight.
If $200+ is a bit beyond your budget, you may also wish to consider one of the many shareware screenplay formatting tools which are floating around. One of the best is Screenpro, which is a screenplay formatting template for Microsoft Word (compatible with all versions from Word 97 on). Screenpro provides a range of macro functions to take the drudgery out of formatting screenplays, and for USD $10 registration it isn't going to break the bank. Another good shareware option is ScreenForge, which has been developed to conform to the Hollywood screenplay formatting guidelines laid down in "The Complete Guide To Standard Script Formats Part I: The Screenplay," by Hillis R. Cole, Jr. and Judith H. Haag.
You should also check out the filmmaking.net Toolshed for more screenwriting shareware and freeware options.