NetTime - nettime is a time & attendance software solution.
Toggl - Toggl is an online time tracking tool. It features 1-click time tracking and helps you see where your time goes. Free and paid versions are available.
Meinberg NTP - NTP client and server download for different operating systems.
Harvest - Simple time tracking, fast online invoicing, and powerful reporting software. Simplify employee timesheets and billing. Get started for free.
Atomic Clock Sync - download the free atomic clock sync config utility to optimize how your Windows pc receives updates from time servers
RescueTime - Time management software that shows you how you spend your time & provides tools to help you be more productive.