RemeIO is a web application that we have been working on, which allows you to schedule email reminders.

With RemeIO you can create instant email reminders. It's free, and no sign up is required, it works straight from the landing page. Just provide the reminder's text, due date, your email address and you're done.  You can also create reminders for multiple people (clients, friends, family). 
You can schedule the reminder using natural language, so you can create reminders faster and in a more human way.
RemeIO is about taking the tasks out of the way by scheduling them to be only seen when they need to be dealt with.  Whether it's a birthday, anniversary, meeting or other appointment you can forget about it and RemeIO will remind you at the right moment.