Free Alarm Clock - Free Alarm Clock is a free, full-featured and user-friendly computer alarm clock for Windows.
Right Inbox - Schedule Emails in Gmail To Be Sent Later
Gnome Clocks - Clock application designed for GNOME 3
Recurrr - Send recurring emails
AlarmDJ - Online Alarm Clock - Use YouTube videos or MP3 files as alarm sound. Works offline.
FollowUpThen - The simplest way to schedule an email reminder