Searching FOSS project management software

I have begun the search for a software application to manage project tracking and collaboration. It will need to be browser based so I can have it used internally and externally for Aura Media. Using PHP as the scripting language is the preference as that is what I am most comfortable with, but I am not against a solution that used Python or Ruby. The last requirement is a free and open source license.

In the past I have been a happy Mantis user for bug and issue tracking. So much that I have installed it in a few client sites. However now I want a broader product that includes time tracking and more collaboration features. Also Mantis is showing its age in a visual sense, and this can put off less technical users. Project tracking is the aim, not project planning with features like gannt charts.

In the past I did look at ActiveCollab, but they changed their license, and Streber, but it was immature and moving in a more wiki direction.

My current investigation list is:

Open to any other suggestions.