The importance of project management tools is almost never fully appreciated. I am shocked at how common it is for a group of developers to go working without version control, ticket tracking, development documentation and so on. The very first thing I do when working with a new client is to make sure that they get these tools in place if they haven't already.
Those who are used to working without a complete set of project management tools never fail to appreciate the benefits of them once they are introduced. I consider it next to impossible for a team to work together without managing code and tasks in an efficient and highly organized way.[img_assist|nid=155|title=|desc=|link=none|align=right|width=250|height=156]
Hopefully you do not need to be sold on this idea and are using CVS or SVN to manage your project already. You likely have some sort of ticket system. It is a little less likely that you have both of these components integrated with each other.
When it comes to choosing a solution for project management software, a die-hard Drupal user has a dilemna. On one hand, Drupal seems as though it should be the perfect solution. It's fully customizable, has lots of nifty project management related modules and, most importantly, it's Drupal! Why would you not use it? "Eating your own dogfood" is the way to go, right? Meh...