Simple bug tracking and issue tracking tool. It so simple, it’s like sticky-notes for your website.
Mantis Bug Tracker
MantisBT is an open source issue tracker that provides a delicate balance between simplicity and power.
DebugMe is a visual feedback, issue tracking & project management solution which saves time and frustration for everyone during a website project.
Bugzilla is a robust, featureful and mature defect-tracking system or bug-tracking system. Defect-tracking systems allow teams of developers to keep track of outstanding bugs, problems, issues, enhancement and other change requests in their products effectively.