HUZZAR!
It's the return of the ol' writing software thread!
I'll start. Movie Magic 2000 is the best. All the others suck, royal!
Seriously, any word processor will do the job. Some software have formats already built in so you can do a movie script in the correct layout very easily, but even the standard word processors can set tabs or macros for that.
They managed with typewriters before we had this fancy technology to complicate the process.