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.
Clockify - Simple and free time tracker. Perfect for small and mid-sized businesses as well as freelancers. Unlimited projects and users, unlimited productivity. Get all the premium functionalities, completely free.
Hubstaff - Simple yet powerful employee work tracker with screenshots, timesheets, billing, in-depth reports, and more. Understand productivity issues and act on them.
Cattr - Cattr is a free open-source self-hosted time tracker with desktop clients for windows, mac, linux.
Time Doctor - Time Tracking and Time Management Software that is accurate and helps you to get a lot more done each day.