There’s a forum on the official Script Frenzy site where people are listing out their choices for script writing software they’re going to use. It’s very helpful and you should check it out. It has many options for people wanting to pay and people who might be strapped on cash and are taking the free option.
In another post I mentioned Scripped, which is an amazing site. Similar to is is Zhura which in my opinion offers more features and is nicer to use, but I know some people prefer the simper format of Scripped.
What I’ve now converted to is Celtx. Yes, you have to download it, but I would highly recommend it. I downloaded it for test, not actually expecting to use it, and I fell in love.
You can use Celtx to format stageplays, films, comic books, and other forms of media. It’s simple (it’s free) and they provide many means of organization within it. If you decide to use Celtx I would recommend looking at the example of whatever you’re writing that they give you. I was able to find out about many features using this.
So I’m just going to link Celtx on the side since that’s what I’m using, but the other sites mentioned are linked in this post, and you can always check out the software thread at Script Frenzy.