Day One - A simple journal application for the Mac, iPhone, and iPad. AboutTo learn more about Day One, see these two excellent reviews . PublishPublish is not available in Day One 2.
Future Me - Send an email to your future self
Journalistic - A simple, yet powerful micro journaling app
Letter to Yourself - Send a physical letter to your future self
Happyfeed - A simple gratitude journal for iOS
Dabble Me - Your own private place to write. A journal/diary to help you remember what's happened in your life.