Ticket Tracking Software
A Perl based software bug tracking system which can also be used for help desk support. Used by the Mozilla Foundation, creators of FireFox.
Perl and MySQL or PostgreSQL
A trouble ticket system to track telephone calls and e-mails. Designed to allow your support, sales, pre-sales, billing, internal IT, and helpdesk to operate in one system. OTRS is open sourced under the GPL and is written in Perl.
Perl and MySQL, PostgreSQL, Oracle or SQL Server
RT: Request Tracker
RT is an open source ticket tracking tool. It's primary interface is email with a web back end for administrators. RT has been under development since 1996.
Perl and MySQL, PostgreSQL or Oracle
Minimalistic web based project management and bug tracking tool. Trac also includes wiki functionality. Written in Python.
Python and SQLite, PostgreSQL or MySQL
Zentrack is a help desk, bug tracking, and project management system.