With NudgeMail, setting up reminders is as easy as sending an email. You set up a reminder based on how you address your note, or by the subject you use in your message. They claim to be able to recognize just about any format for your reminder, whether you set it for “2 hours from now”, “Monday”, or “January 10”. All you need to do is to send your message from an account you monitor regularly, since that’s the email address your reminder will be sent to. It’s got some good utility functions as well, allowing you to “snooze” a reminder so that it’ll come back later, as well as looking over a list of your pending reminders.
NudgeMail is a free service. You don’t need to register, so there are no account names or passwords to have to keep track of. You’ll need a web browser and an email address to use it.