Sleep Cycle - Bio-alarm clock that wakes you up at optimal times based on your sleep patterns.
Free Alarm Clock - Free Alarm Clock is a free, full-featured and user-friendly computer alarm clock for Windows.
Sleep Time - Alarm Clock - Sleep Time provides insight into your sleep patterns. By tracking your level of movement throughout the night, Sleep Time generates customized sleep data in easy-to-read charts.
Gnome Clocks - Clock application designed for GNOME 3
Sleep Calculator - Want to wake up in a good shape?
AlarmDJ - Online Alarm Clock - Use YouTube videos or MP3 files as alarm sound. Works offline.