Winterboard - Give your iPhone or iPod Touch a graphical overhaul!
Free Alarm Clock - Free Alarm Clock is a free, full-featured and user-friendly computer alarm clock for Windows.
Springtomize - Tear down the walls
Digital Clock 4 - Beautiful customizable clock with plugins
Dreamboard - DreamBoard lets you take control over the homescreen of your jailbroken iPhone.
AlarmDJ - Online Alarm Clock - Use YouTube videos or MP3 files as alarm sound. Works offline.