LiquidPlanner is a great tool for Getting Things Done enthusiasts and project managers in general. It allows you to break down your project into multiple steps with best/worst case time scenarios and then gives you a complete picture of the project timeline and tasks in an easy to understand format. The reminders are fantastic! I have used it has a professional with a paid account, and also as a university student with a free academic account. I have used the timer function to record how much time I am spending on a task so that I can bill clients or to just to have it for future reference, it's a nice feature! Uploading documents really makes sharing and keeping things in a central location very handy.
