Free Alarm Clock - Free Alarm Clock is a free, full-featured and user-friendly computer alarm clock for Windows.
Digital Clock 4 - Beautiful customizable clock with plugins
Gnome Clocks - Clock application designed for GNOME 3
AlarmDJ - Online Alarm Clock - Use YouTube videos or MP3 files as alarm sound. Works offline.
Alarm Clock Pro - iTunes alarm clock, stop watch, timer, and more!
Alarm Clock (applet) - Alarm Clock is a fully-featured alarm clock for your GNOME panel or equivalent.