Power Alarm Clock - Free - Powerful alarm android app to manage even the most complex requirements.
T-Clock Redux - T-Clock Redux in an enhanced fork of Stoic Joker's T-Clock 2010 with ISO week number support...
AlarmDJ - Online Alarm Clock - Use YouTube videos or MP3 files as alarm sound. Works offline.
Gnome Clocks - Clock application designed for GNOME 3
DS Clock - Keep your time synchronized with Atomic Time servers, using customizable digital desktop clock with westminster chimes.
Alarm Clock (applet) - Alarm Clock is a fully-featured alarm clock for your GNOME panel or equivalent.