Fluidtask

Fluidtask is a free, flexible task manager. Originally created over a weekend because Steven was unhappy with all the other task/project management options he could find, it's since been refined and put up for the public to use.

Unlike most task tracking applications, fluidtask only asks the task's name, and a range of how long it should take. Then, as users order their tasks by priority, fluidtask automatically calculates when they can expect to finish a project, and what they should work on next. It's like having a scheduling assistant, that always tells you the truth. After months of use, fluidtask's estimated deadlines have always been within a day of when the work was actually completed, regardless of project size.

Sound interesting? check it out!