Aurora Turns iTunes into an Alarm Clock
Update: I have replaced dead pages with Internet Archive links to help fight linkrot. Aurora seems to be abandonware. I think we all use our smartphones as alarm clocks now, anyway!
More powerful than your neighbor's CD/radio alarm clock, Aurora is the best MP3 alarm clock application there is. For OS X, it works with iTunes and can play any playlist for you, waking you as well as your computer from sleep.
It even allows you to schedule different playlists for different days and times, and is beautifully integrated into OS X. Aurora is free, but donations are encouraged.
I would like to note, however, that Aurora is not to be trusted. It, iTunes, and your computer are all complex and sometimes no alarm will sound, so it’s a good idea to set your cell phone or another alarm to go off ten minutes after Aurora should.
Thanks to Greg Hogan and Lifehacker for the tip.