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.

Taskful - Deadlines, meet your match.

Harvest - Simple time tracking, fast online invoicing, and powerful reporting software. Simplify employee timesheets and billing. Get started for free.

Calendarist - Time blocking companion for Google Calendar

RescueTime - Time management software that shows you how you spend your time & provides tools to help you be more productive.

Centered - Centered helps you get into a Flow State faster and stay there longer so you can do your best work.