Future Me - Send an email to your future self
Toggl - Toggl is an online time tracking tool. It features 1-click time tracking and helps you see where your time goes. Free and paid versions are available.
Letter to Yourself - Send a physical letter to your future self
Harvest - Simple time tracking, fast online invoicing, and powerful reporting software. Simplify employee timesheets and billing. Get started for free.
Dabble Me - Your own private place to write. A journal/diary to help you remember what's happened in your life.
RescueTime - Time management software that shows you how you spend your time & provides tools to help you be more productive.