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Check out Final Draft. It's a glorified word processor that formats your screenplay into film industry standard format. I've never used it myself, but I hear it's pretty good.
 
Final Draft and Movie Magic Screenwriter ( http://www.screenplay.com/ ) are the "Coke" and "Pepsi" of screenwriting software packages. My impression is that Final Draft probably is somewhat more popular with most writers, whereas I think Screenwriter at least used to be found more in studios because they also had Movie Magic's production scheduling and budgeting software.

You'll find plenty of endorsements for both apps. I don't think you can really go wrong with either one.

The "bible" of format is Cole and Haag's "Complete Guide to Standard Script Formats, Part 1: The Screenplay".

http://www.amazon.com/gp/product/0929583000/ref=pd_cmp_rvi_1/103-2664386-2971861?n=283155

You can find plenty of examples of format on the Web, too, if you look. It definitely isn't the same as theatrical plays.

Also a good idea to get your hands on some real scripts; the book versions of movie scripts you find in bookstores are not usually formatted the same as real scripts.

Good luck!
 
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Celtx, Textmate & Links

I found this to be helpful as I am switching to OS X and haven't yet purchased the memory to run Parallels with Win XP

Celtx and Textmate are both decent programs. Celtx looks like it could become the industry standard. Final Draft is too expensive (proprietary ********) and at this time it is difficult to import/export without going throught the script and making corrections.

The link below was very helpful

http://en.wikipedia.org/wiki/Screenwriting_software

All of these processors format for you
 
Although I recognize that OnceUGoMac is correct about Final Draft, it is a little expensive.

I did check out Celtx, and it looks great! Thanks to thespiderprince for suggesting it!
 
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