KuKu Klok is a pretty straightforward webapp—you set a time for an alarm to go off, you choose a sound to wake up to, and you hit "Set Alarm." Kind of like the Online Alarm Clock, but the neat...
Windows only: iSnooze provides the same kind of iTunes-as-alarm-clock functionality as the Mac-only Alarm Clock 2, but lets you get a lot more specific about your wake-up parameters. Wake up to a...