Free Alarm Clock - Free Alarm Clock is a free, full-featured and user-friendly computer alarm clock for Windows.
Reminder Commander - Reminder manager that reminds you about important events in advance.
Gnome Clocks - Clock application designed for GNOME 3
Date Reminder - Date Reminder reminds you of recurring or nonrecurring events, like birthdays, bills to pay...
AlarmDJ - Online Alarm Clock - Use YouTube videos or MP3 files as alarm sound. Works offline.
Scheduled tasks - GNOME GUI for configuring a users' cron (automatic jobs). Some of its features are: