I have used a variety of issue tracking systems, but I have recently
converted them ALL to the Rails based Redmine.
It is still a bit young, but it has nearly everything I am looking
for.
* GPL Licensed
* Clean User Interface
* Easy Setup & Administration
* Multiple projects support
* Flexible role based access control.
* Flexible issue tracking system
* Gantt chart and calendar
* News, documents & files management
* Feeds & email notifications.
* Per project wiki
* Per project forums
* Simple time tracking functionality
* Custom fields for issues, projects and users
* SCM integration (Specifically SVN, but also supports CVS, Git,
Mercurial, Bazaar and Darcs)
* Multiple LDAP authentication support
* Multiple databases support
* Time Tracking
It also has some interesting plugins, such as the ability to have
integrated timesheets.
Check out the details
http://redmine.org
Or take it for a test drive
http://demo.redmine.org
~Alan