Wordzen - We write your emails for you. Literally.
SendRecurring - SendRecurring allows you to setup, send, and maintain scheduled email reminders.
InboxVudu - Spend 90% less time on e-mail.
Recurrr - Send recurring emails
Mailbutler - Mailbutler adds lacking functionality to email clients and increases your productivity
FollowUpThen - The simplest way to schedule an email reminder