Alarm Clock S.E. is the ultimate alarm clock for OS X. With its complex alarm system, you will be able to create alarms that fit even the most complicated schedules. Wake up to songs, run shell and applescripts whenever you want, and never miss an appointment again.
Now new in S.E., your computer will wake from sleep or turn on as necessary so you'll never miss an alarm again!
Note: The download link is for 10.3 and above, for 10.2 and below see the homepage.