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.
Harvest - Simple time tracking, fast online invoicing, and powerful reporting software. Simplify employee timesheets and billing. Get started for free.
Qbserve - Freelance time tracking, invoicing, and productivity improvement
Bonsai - One platform to streamline your entire business
Pomodone - Pomodone is the easiest way to track your workflow using Pomodoro technique, on top of your current task management service.
Timing - Timing is the best way to keep track of the time you spend with your Mac.