David Goodwin has pointed out a new open source project that the PalePurple group are releasing - the Virtual Planning Board.
It's basically a piece of web-based software, written in Python and PHP, that allows you to allocate tickets from multiple Trac projects to a simple week-based 'board' in order to organise work priority for developers.
I've written about why we wanted this, and created a short user guide on the Trac site for the project. This is still in development and we're working on some more features (You can see what we've got planned from our timeline).
It's been released under the GPL and has a Subversion repository where you can grab the latest code from. There's also an installation guide that's been developed to help you get started.