Harvest - Simple time tracking, fast online invoicing, and powerful reporting software. Simplify employee timesheets and billing. Get started for free.
Todoist - Todoist is a to-do list that helps you get organized, at work and in life.
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.
TaskPaper - Plain text to-do lists for Mac
Pomodone - Pomodone is the easiest way to track your workflow using Pomodoro technique, on top of your current task management service.
Microsoft To-Do - Task management tool