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.
Todoist - Todoist is a to-do list that helps you get organized, at work and in life.
Paymo - Manage projects, track time, create invoices, and get paid online.
Todo.txt - Track your tasks and projects in a plain text file, todo.txt. A todo.
ManicTime - Track your computer usage and use collected data to accurately tag time.
EssentialPIM - EssentialPIM is a free Personal Information Manager that keeps up with the times and lets you manage appointments, tasks, notes, contacts, password entries and email messages across multiple devices and cloud applications.