Zoho BugTracker!

Trusted by 11,000+ businesses, JIRA is the leading bug tracking, issue tracking and project management tool. JIRA combines issue tracking, agile project management, customisable workflow, and a pluggable integration framework to increase the velocity of your software development team.

Phabricator is a collection of open source web applications that help software companies build better software.

osTicket is a widely-used open source support ticket system. It seamlessly integrates inquiries created via email, phone and web-based forms into a simple easy-to-use multi-user web interface. Manage, organize and archive all your support requests and responses in one place while providing your customers with accountability and responsiveness they deserve.

Mantis Bug Tracker is a free and open source, web-based bug tracking system. It is written in the PHP scripting language and works with MySQL, MS SQL, and PostgreSQL databases and a webserver. MantisBT can be installed on Windows, Linux, Mac OS, OS/2, and others. Almost any web browser should be able to function as a client. Moreover MantisHub is available as commercial hosted solution of MantisBT.

Team Clerk is project and task management software that automatically keeps your team organized and monitors progress of all of your projects and tasks. Let us organize what you do,so you can focus on why you do it.

Tracker is a story-based project planning tool from Pivotal Labs that allows teams to collaborate and react to real-world changes instantly. Its based on agile software methods, but can be used on a wide range of projects.

Bugzilla is a "Defect Tracking System" or "Bug-Tracking System". Defect Tracking Systems allow individual or groups of developers to keep track of outstanding bugs in their product effectively. Most commercial defect-tracking software vendors charge enormous licensing fees. Despite being "free", Bugzilla has many features its expensive counterparts lack. Consequently, Bugzilla has quickly become a favorite of hundreds of organizations across the globe.

Simple, high-reliability, distributed software configuration management. Fossil is a distributed version control system, bug tracking system and wiki software server for use in software development.

The Bug Genie is an issue tracking and project management, completely free for small teams.

PMRobot combines Bug Tracking + Client Collaboration + Agile Project Management Software.

Flyspray is a lightweight, web-based bug tracking system written in PHP for assisting with software development and project managements. Originally developed for the Psi Jabber client project it has been made available to everyone under the LGPL 2.1 licence. Flyspray aims to cut out the unnecessary complexity of other bug trackers focusing on a very intuitive design making it very easy to effectively manage projects.

FogBugz manages projects, tracks bugs, and even tells you when you’re going to ship. It includes an issue tracker, advanced project management and scheduling, a wiki, and customer support features like email routing and discussion groups. It is completely extensible with plug-ins and an XML API, and integrates with all major version control systems.