futureme.org is a website created by Matt Sly and Jay Patrikios that gives you the ability to send yourself an email at a future date and time.
A quick look at their site gives the impression that many people are using this service in a very introspective sort of way. They are using it to help kick a habit (like quitting smoking), establish a habit (like start smoking), or continue working toward certain goals in their life (smoke more!).
I am sure that there people using this to email very utilitarian items as well. Rather than sending myself a message to the future likes “exercise more”, I might just as well remind myself “My landlord mentioned that she might consider selling the condo we are renting in the Spring. Remind her that we would be very, very interested.”
I can also see myself using it as a snarky way to interact with my future self, and simply playing it for laughs. “Hey, future-self. Decided to go out and get a tattoo of a unicorn farting out rainbows into the open mouth of a skull. Let me know if that was a good call.”
Now if only we could send an email BACKWARDS through time. I would have sooooo many uses for that...