This module is currently in alpha. Use at your own risk.
Case Tracker is an excellent and extensible project management module that is notably a core component of Open Atrium. With the help of the Feeds module, we can now share cases across multiple sites.
Original feature request issue: http://drupal.org/node/826490
The original use case for this module required the ability to set up groups in Open Atrium with a choice of project "templates" with pre-populated cases. The projects and cases required a number of additional fields and so View Datasourse and Feeds XPath Parser allow for this in a very flexible fashion, via XML. This could, eventually, allow for importing from alien project management tools, such as Redmine.
Default views and feed importers are provided, so this module is fairly straight-forward to setup. Documentation is currently lacking, due in part to a lack of time on my part, but also to my lack of perspective. That is, it all looks pretty obvious to me, but then I know where everything is. Please file issues to help me fix it.