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.

Todo.txt - Track your tasks and projects in a plain text file, todo.txt. A todo.

Hubstaff - Simple yet powerful employee work tracker with screenshots, timesheets, billing, in-depth reports, and more. Understand productivity issues and act on them.

Task Coach - Task Coach is a simple open source todo manager to keep track of personal tasks and todo lists.

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.

Strikethru - Strikethru is a kind of to-do list notebook for managing work lists and staying updated with the important tasks.