Bug Tracking

Help Desk in the Cloud . . .

Trac (Py)

Mantis

Redmine (Ruby)
RT RTIR (Perl)
Bugzilla (Perl)
openCRX (Java)
TrackPlus (Java)
SD (Perl)
Roundup (Py)
GForge
Flyspray

Autres (closed source)

Jira (Java par Atlassian, gratuit mais pas libre) + !Workflow
Fogbugz
Eventum

Discussion

http://www.dmoz.org/Computers/Software/Configuration_Management/Bug_Tracking/Free
http://en.wikipedia.org/wiki/Comparison_of_issue_tracking_systems#Bug_tracking_systems