Mail to the Future is a just-for-fun service which allows you to send mails to your friends, which will be delivered in the future. (i.e) You can choose it to be delivered tomorrow, next month, next year or even after more years. Thats cool and can be pretty useful under some circumstances.

Mail a Stranger is another service by the same team. It is even more fun. It lets you send (and receive) messages to (and from) total strangers. That would be great as we can meet some new people 8)