I have been using "scrivener" and quite like it. There's a very similar program for windows called "liquid binder"-- anyone messed around with these?
I use Liquid Story Binder. It's the worst name for probably one of the best pieces of writing software around (equivalent to or right behind Scrivener.)
It can be overwhelming to people at first because there are so many features available, but what they don't realize is you only use what's useful to you and it's great. You can grow into it at your own pace, or use different features for different projects. Unlike other pieces of writing software, it's a set of tools, not a process or workflow instrument.
I wrote about it on my practice blog
here. And there are screenshots!
Also, forgot to mention. The developer is super-supportive of the writing community and is constantly enhancing the product based on user feedback and you can download and try it for free for 30 days.