Okay, so this isn't strictly a development tool, but Gantt Project has a pretty nifty, free, project management application.

With GanttProject you can break down your project into a tree of tasks and assign human resources that have to work on each task. You can also establish dependencies between tasks, like "this task can't start until this one is finished". GanttProject renders your project using two charts: Gantt chart for tasks and resource load chart for resources. You may print your charts, generate PDF and HTML reports, exchange data with Microsoft(R) Project(TM) and spreadsheet applications.

The site also mentions a good point with regards to Project:

• Good (and growing!) set of basic features. This set is enough for most people (remember that 80% of MSProject customers use 20% of it's numerous features)
• Easy learning. You don't need thick manuals to start working with GanttProject. If you are familiar with the notion of tasks, assignments and dependencies, you'll become an expert in GanttProject in a couple of hours.

Check it out if you're in the market for a free, simple, task based project management.