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.
TopTracker - Beautiful, free time tracking
Deputy - Deputy is a software for employee scheduling, time and attendance and communication management.
Cattr - Cattr is a free open-source self-hosted time tracker with desktop clients for windows, mac, linux.
QuickBooks Time - Easily track time for effortless payroll, invoicing, and job costing—without the paperwork, guesswork, or hard work.
timeBuzzer - timeBuzzer enables freelancers and project-driven teams to track their time at the touch of a button, understand where their time goes and create reports with just a few clicks.