Retrospectiva is another bug tracking / project management tool. It’s got an intersting approach that I’m interested in. From their home page:
Retrospectiva is an open source, web-based, project management and bug-tracking tool. It is intended to assist the collaborative aspect of work carried out by software development teams through the use of blogs, a wiki and tickets.
Users open tickets to track bugs, and request enhancements. Administrators set targets for the team through milestones. A milestone is considered completed when all tickets assigned to it are closed. The wiki is used for the documentation of the project, whilst the blog logs ongoing progress. When used in conjunction, these tools provide a helpful framework for developing and maintaining source code. The generated code can be browsed directly in Retrospectiva, and changesets record updates made to the source repository.
It’s built with Ruby on Rails. I really like their workflow, and the UI’s not half bad either.
Fijiaaron 
The really interesting thing on their website is their use of Passenger + Apache for RoR. I think passenger is a new “mod_ruby” style approach.
Here’s some interesting stats about Passenger and Ruby Enterprise Edition
http://www.rubyenterpriseedition.com/comparisons.html
The REE memory footprint looks very interesting indeed if it lives up to it, which Retrospectiva sounds happy with.