Using your Mac to wake you up isn't a new idea, but I think it is a good idea. iRooster 2.2 (release notes) is another alarm clock app that turns your Mac into the most expensive alarm clock you have ever used. It allows you to pick playlists, or random songs, from your iTunes library to jar you awake from slumberland. It will also download album art if the track it is playing has no artwork associated with it.
New in version 2.2 is an iTunes like style for the clock (not pictured above) and some bug fixes for those of us on Intel Macs. iRooster requires iTunes 6.0 or above and OS X 10.3 or above and will set you back $9.95.