I've been fiddling with Redmine in the past few days and not 100% happy with the way it organises tasks etc.
I need a open source PHP based solution that is like Redmine or even VersionOne to assist our small team of 3 developers with project management.
We basically use Scrum, and would love to be able to create projects, break them down into user stories, and then further break stories down into tasks.
We typically use also size tasks and user stories using the PERT analysis formula.
For open source Scrum tools information (list of tools, reviews), you should look at http://www.opensourcescrum.com/