Remindly - Simple and user friendly, open-source reminder app for Android.
Free Alarm Clock - Free Alarm Clock is a free, full-featured and user-friendly computer alarm clock for Windows.
KTeaTime - KTeaTime is a handy timer for steeping tea. No longer will you have to guess at how long it takes for your tea to be ready. Simply select the type of tea you have, and it will alert you when the tea is ready to drink.
Digital Clock 4 - Beautiful customizable clock with plugins
Alarm Clock Xtreme - Alarm Clock Xtreme: Alarm, Stopwatch, Timer (Free) is the most popular alarm clock app created and published by AVG Labs for both iOS and Android devices.
Gnome Clocks - Clock application designed for GNOME 3