iSleep features a sleep timer coupled with an optional Alarm Clock for iTunes and DVD Player. Just choose for how long you'd like to listen to your music, and, if you want to, set up the alarm clock ; iSleep will care for the rest.
iSleep is very easy to use; nevertheless, it has lot of features. You can, for example, ask iSleep to put your Mac to sleep after the end of the music, and to wake it up in the morning : it can be useful if your Mac is noisy ! But that's just the beginning of the story... More Info »
If you Mac has a DVD player, you can also ask iSleep to use a DVD instead of playing music. iSleep will automatically put your Mac to sleep (or shut down it, quit the DVD player... there are many options available) when the movie is over !