Right Inbox - Schedule Emails in Gmail To Be Sent Later
Digital Clock 4 - Beautiful customizable clock with plugins
Recurrr - Send recurring emails
System Scheduler - System Scheduler for Windows, Free Task Scheduler Software replace Microsoft Windows Task Scheduler
FollowUpThen - The simplest way to schedule an email reminder
VisualCron - VisualCron is an automation, integration and task scheduling tool for Windows.