fcron - Fcron is a scheduler designed for Unix/Linux systems, especially usefull when your system is not up all the day long.
AlarmDJ - Online Alarm Clock - Use YouTube videos or MP3 files as alarm sound. Works offline.
incron - This program is an "inotify cron" system. It consists of a daemon and a table manipulator.
T-Clock Redux - T-Clock Redux in an enhanced fork of Stoic Joker's T-Clock 2010 with ISO week number support...
mcron - mcron is GNU's implementation of cron. It is a 100% compatible replacement for Vixie cron.
ClocX - ClocX - freeware analog clock for Windows desktop with many features like calendar, alarms, skins, antialiasing and transparency.