At Freelock our project management tool of choice is Open Atrium.
OpenAtrium is an online collaboration and task-management suite built on top of Drupal. Like Drupal, it is completely modular, so the feature set can be changed and expanded to meet the needs of a wide variety of applications. Out of the box it has support for case management, collaborative document editing, shared blog and microblog, and a variety of user-configurable dashboard views.
The main advantage of Open Atrium over more traditional project management tools is how well it fosters both collaboration and communication within a team. It's web-based, multi-user, easy-to-use, and can be configured to easily allow users very granular access to functions associated with any number of different roles.
At Freelock we utilize Open Atrium as our project management tool. Let us know if you have any questions.