SendRecurring - SendRecurring allows you to setup, send, and maintain scheduled email reminders.
Future Me - Send an email to your future self
Recurrr - Send recurring emails
Letter to Yourself - Send a physical letter to your future self
FollowUpThen - The simplest way to schedule an email reminder
Dabble Me - Your own private place to write. A journal/diary to help you remember what's happened in your life.