Crontab UI - Easy and safe way to manage your crontab file
FollowUpThen - The simplest way to schedule an email reminder
Scheduled tasks - GNOME GUI for configuring a users' cron (automatic jobs). Some of its features are:
Simply Remind Me - Free email and text reminder service so you don't forget the important things in life!
024h Lucky Reminder - 024h Lucky Reminder is a reminder software for home and office.
Auto Mail Sender - Auto Mail Sender Standard Edition official page. A powerful and easy-to-use eMail scheduler.