Hourglass - Hourglass is the most advanced simple countdown timer for Windows.
Timer Tab - Online countdown timer, alarm clock, and stopwatch.
Alinof Timer - Alinof Timer is a very easy to use timer for your Mac.
Gestimer - For those little reminders during the day
CookTimer - CookTimer is a simple cross-platform countdown timer that helps when cooking, making tea or eggs.
Online Stopwatch - Online Stopwatch is free to use online tool that allows you to keep track of the important events and tasks that you are performing.