Amazing Marvin - Customizable personal productivity tool
Timer Tab - Online countdown timer, alarm clock, and stopwatch.
Focusmate - Distraction-free productivity via virtual coworking
Gestimer - For those little reminders during the day
Social Pomodoro - Meet an accountability buddy for 25 minutes of focused work.
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.