There's a lot of discussion in the writing world about writing tools. Some people use open source tools like Scribus or Storybook. Other people use Microsoft Word or Google Docs, so they can access their work from any computer. Microsoft Word is rife with problems (and expensive!), and I don't like the functionality of Google Docs, although it works in a pinch. For me, it's Scrivener, because the design just makes sense. I can compile research, work in multiple documents, arrange them on my cork board and eventually compile everything into a standard manuscript format. And if I ever decide to write screen plays or non-fiction, there are formatting options for that too.
Which writing tools do you use?