like jira but free!

Are you working with open source tools?
Is your configuration management tool svn/subversion?
If you answer yes, then you might consider using jira and twiki in your project.
Jira, a very nice tool to use comes with a price tag.
So for users like me, who love the word "free" aka "open source" (better then free), here is a tool that offer many jira like features while integrating a wiki in it.

Here is a quick look at features:
- wiki like collaboration
- subversion integration
- Ticket/bug tracking

@link to website
@ rubyonrails uses it