Harvest - Simple time tracking, fast online invoicing, and powerful reporting software. Simplify employee timesheets and billing. Get started for free.

Clocker - Keep track of people in different time zones

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.

Dato - Better menu bar clock with calendar and time zones

Pomodone - Pomodone is the easiest way to track your workflow using Pomodoro technique, on top of your current task management service.

Clock mini - Simple clock app in the Dock