I created this section to answer questions about Bugzilla competitors and variants, then found a wonderful site which covers an awful lot of what I wanted to discuss. Rather than quote it in its entirety, I'll simply refer you here: http://linas.org/linux/pm.html

Red Hat Bugzilla is probably the most popular Bugzilla variant on the planet. One of the major benefits of Red Hat Bugzilla is the ability to work with Oracle, MySQL, and PostGreSQL databases serving as the back-end, instead of just MySQL. Dave Lawrence has worked very hard to keep Red Hat Bugzilla up-to-date, and many people prefer the snappier-looking page layout of Red Hat Bugzilla to the default Mozilla-standard formatting. URL: http://bugzilla.redhat.com/bugzilla/

Fenris can be found at http://fenris.lokigames.com. It is a fork from Bugzilla.

Issuezilla is another fork from Bugzilla, and seems nearly as popular as the Red Hat Bugzilla fork. Some Issuezilla team members are regular contributors to the Bugzilla mailing list/newsgroup. Issuezilla is not the primary focus of bug-tracking at tigris.org, however. Their Java-based bug-tracker, , is under heavy development and looks promising! URL: http://issuezilla.tigris.org/servlets/ProjectHome

Scarab is a promising new bug-tracking system built using Java Serlet technology. As of this writing, no source code has been released as a package, but you can obtain the code from CVS. URL: http://scarab.tigris.org

Although Perforce isn't really a bug tracker, it can be used as such through the jobs functionality. http://www.perforce.com/perforce/technotes/note052.html

SourceForge is more of a way of coordinating geographically distributed free software and open source projects over the Internet than strictly a bug tracker, but if you're hunting for bug-tracking for your open project, it may be just what the software engineer ordered! URL: http://www.sourceforge.net