Future Me - Send an email to your future self
Task Coach - Task Coach is a simple open source todo manager to keep track of personal tasks and todo lists.
Letter to Yourself - Send a physical letter to your future self
Flashnote - Flashnote is a quick notes manager
Letter to my future self - Letter to my future self is a prominent email scheduling service that gives you the opportunity to create a letter with goals and thoughts for your future self and schedule a date for sending it.
Tot - Convert any text into a Trello task