Hourglass - Hourglass is the most advanced simple countdown timer for Windows.
Actuflow - App for checking why you use your smartphone before using it
SnapTimer - SnapTimer is a simple, free, portable countdown timer for Windows.
Tockler - Automatically track applications usage and working time.
Free Countdown Timer - Free Countdown Timer is a free, full-featured and user-friendly countdown timer for Windows
RescueTime - Time management software that shows you how you spend your time & provides tools to help you be more productive.