Pages - Pages for Mac is a word processor that offers tools needed to create documents.

Apple iWork - iWork is an office suite by Apple.

Scrivener - Scrivener is a content-generation tool for composing and structuring documents.

Google Docs - Create a new document and edit with others at the same time -- from your computer, phone or tablet. Get stuff done with or without an internet connection. Use Docs to edit Word files. Free from Google.

Ulysses.app - A powerful writing tool for Mac, iPad, and iPhone

Airborn - Create and edit documents online without sacrificing your privacy