This is way cool: at FutureMe.org, you can compose an e-mail (for free) to your future self and they'll send it on any day you choose, as late as 2037.
I LOVE this idea. What a cool pick-me-up, one average day to receive an encouraging e-mail from your past self. I'm thinking I'll for sure need one on my 30th birthday (looming ever closer). In 2037 I'll be 54. How strange-yet-awesome to get an e-mail from my 26-year-old self...assuming, of course, I still have the same e-mail address.
What would you include in an e-mail to your future self? I think I'd write in plenty of encouragement; beyond that, I'm not sure.