Memo to Me - Online email & SMS reminder service.
Free Alarm Clock - Free Alarm Clock is a free, full-featured and user-friendly computer alarm clock for Windows.
Simply Remind Me - Free email and text reminder service so you don't forget the important things in life!
Digital Clock 4 - Beautiful customizable clock with plugins
Kana Reminder - Kana Reminder is a program which can be used to set a reminder to be triggered at a specified time.
AlarmDJ - Online Alarm Clock - Use YouTube videos or MP3 files as alarm sound. Works offline.