Hourglass - Hourglass is the most advanced simple countdown timer for Windows.
T-Clock Redux - T-Clock Redux in an enhanced fork of Stoic Joker's T-Clock 2010 with ISO week number support...
Alarm Clock Tab - Web based time tools including alarms, timers, stopwatch, and time zone converter. Resources also include Tabata, Pomodoro and other useful tips and tactics for managing time and time tracking.
AlarmDJ - Online Alarm Clock - Use YouTube videos or MP3 files as alarm sound. Works offline.
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.
DS Clock - Keep your time synchronized with Atomic Time servers, using customizable digital desktop clock with westminster chimes.