I've been using Scrivener to organize my writing and game projects.
If you're needing ideas, I've read that some people have success with this: http://rpggeek.com/rpgitem/47395/mythic-game-master-emulator
Careful with that. While fixing a bunch of issues in my game I introduced a new and completely unnecessary one because I was so sleepy. And that was right before I pushed that version out for testing. XD