Reminduck - A simple reminder app made for elementaryOS with Vala and GTK. - matfantinel/reminduck
Scheduled tasks - GNOME GUI for configuring a users' cron (automatic jobs). Some of its features are:
Memo to Me - Online email & SMS reminder service.
Kana Reminder - Kana Reminder is a program which can be used to set a reminder to be triggered at a specified time.
Simply Remind Me - Free email and text reminder service so you don't forget the important things in life!
Auto Mail Sender - Auto Mail Sender Standard Edition official page. A powerful and easy-to-use eMail scheduler.