We all need a nudge every now and then to remember to get things done. If email is the centre of your notification universe, Reme.io can help jog your memory by sending you a reminder to do a certain task at a date and time you specify.
The service is perfectly simple. You enter your email address, a brief message for your future self, and a date and time that you'd like to receive it. When that time rolls around, you'll get an email with the reminder. Optionally, you can add multiple recipients, which is handy for letting everyone in a group know that an important event is coming up.