Top Open Source Bug Tracking System
1. Bugzilla
2. Mantis
3. Redmine
4. Fossil
5. Flyspray
6. Request Tracker
7. OTRS
8. EventNum
9. The Bug Genie
10. WebIssues
11. elips -- java
http://elips.sourceforge.net/
http://www.thegeekstuff.com/2010/08/bug-tracking-system/
12. itracker -- java
http://www.itracker.org/
13. carab -- java
http://scarab.tigris.org/
14. jtrac -- java
http://jtrac.info/
15. bugfree -- php
http://www.bugfree.org.cn/
16. more
http://www.webresourcesdepot.com/9-free-and-open-source-bug-tracking-softwares/
Non-Open Source Bug Tracking System
1. JIRA/JIRA Client
2. fogbugz
http://www.fogcreek.com/fogbugz/
2. bugtracker
3. Bugzero
Online
http://www.easy-bugs.com/
