Shameless plug. I always have trouble waking up. Since the Mac App Store came out this year, I've been working on a simple alarm clock app called "Mornings" to do just this (play iTunes or custom MP3s). It actually uses AppleScript to tell iTunes what to play for the iTunes option, so it works with whatever is in your playlists. (The "con" to this is that iTunes automatically opens when the alarm clock plays -- unlike other, more fancy apps, that load the playlists from iTunes but roll their own playback behavior.) Or you can just add your own MP3s and the app won't open iTunes.

I haven't posted it on HN before, but I'd be absolutely grateful if anyone tried it out. As a developer I get some promo codes, so here are some codes (hit Featured, then Redeem to grab it. Or if none of them work, e-mail me and I'd be happy to give you one.)

  F7KTWHLM9H7P 
  3XKY3YEJX9EK
  K63HX7WE9X77
  3RX6ENHL34EE
  WY7X3LRMHKPJ
  JFXETAJH3XYP
  XJXNHTXFEF4P