Future Me - Send an email to your future self
Letter to Yourself - Send a physical letter to your future self
Letterflix - Send letters and snail mail online to the USA, Europe, India, or anywhere in the world. Letterflix is the easiest and secure way to send letters and snail mail anywhere in the world from the comfort of your home.
Futurospective - An app that let's you record messages to your future self
Modern Memories - Letters written today. Delivered in the future.
Jot - The no-fuss way to take notes