TimeMachiner.com is a very convenient site that allows you to send an email today, and have it delivered at a scheduled date in the future.  Excellent for sending birthday greetings etc or for reminding yourself of something you need to do in the future.

The site can also be used like a time capsuler.  Why not email some details of what is happening in your life today and have it delivered to yourself in 5 years time?  You could even email your goals and expectations for the next year and have them emailed to yourself this day next year.