Best Free Project Manager

Open Workbench is a free Open Source project manager that is so feature rich and so powerful that it should at least be considered before any decision is made to purchase a commercial project management package. It's a product that takes time to get your head around.
If you have been using Microsoft Project or other task based manager you'll have to re-orient your thinking because Open Workbench is resource-driven not task-driven.

"An Open Workbench plan is built up from estimates for the tasks of work. Estimates are tied to the resource assigned to the tasks. Duration is then driven by the number of hours each resource will work per week to cover the total number of hours required for the tasks. Open Workbench is best suited for groups that estimate total work effort based on the estimates for all the tasks associated with a project, and then create a staffing plan and schedule for those estimates."

Once you come to terms with this, you will still have to grapple with learning how to use this powerful product. Here is a partial feature list:

• Define projects and create associated work breakdown structures with activities, phases, tasks and milestones
• Create dependencies as finish-start, start-start, finish- finish or start-finish
• Create subprojects and link them to master projects
• Create and manage inter-project dependencies
• Manage advanced task properties such as fixed duration, dependency lag, imposed start/end dates and charge codes
• Schedule tasks manually or automatically using Auto Schedule
• Automatically schedule tasks forwards or backwards
• Schedule across linked master and subprojects
• Schedule to general or individualized calendars
• Define resources as people, equipment, materials or expense
• Assign resources to tasks
• Configure resources on tasks with uniform, fixed, contour, front or back loading
• Track status, percent complete and estimates to complete
• View Gantt charts (both detail and roll-up), PERT charts and the critical path
• Conduct earned value analysis
• Define, compare and reset project baseline setting
• Can read Microsoft Project files

Open Workbench is the real thing, not some amateurish, half baked effort. Like Microsoft Project, it is best suited to large scale projects that can justify the considerable time it takes to learn the product. Those with smaller projects may want to consider some of the simpler (and less powerful) alternatives such as GanttPV or ToDoList.