Literature and Latte's newest application for OS X is called Scapple, and it's now available for download. It's a really helpful utility for visually-oriented users who want to get some ideas down but might feel hampered by traditional outlining tools and text editors that enforce some sort of linear structure.
Scrivener is one of the most well respected, most beloved writing apps on the Mac, one that works the way writers and stories work. For a while now, Scrivener developer Literature & Latte have been working on the highly anticipated iPad version, but issues beyond their control slowed the project. No longer.