"Taskjuggler": http://www.taskjuggler.org/

Taskjuggler is probably the most comprehensive project management tool freely available.

It consists of a backend program that takes input files and generates reports. The are a couple of graphical editor programs with it, but they are more like IDE's. You need to learn taskjugglers language to create projects.


** Pros **

  * The most comprehensive project management software.

** Cons **

  * Own input language discourages editing by others.

  * Some work to hook into our web site perhaps - depending on how we wanted to use it.