Mail2future is an excellent way to send email days, weeks or even months later. You can use it to send a notification to yourself, to share some impressions with yourself older. Also you can congratulate your friend if you are afraid of doing it at the day. I am sure there are many other cases where you can need it.
All you need is to type a subject and a text of your message specifying the delivery day. The service will save your email and send it when the date comes.