Bugzilla is a Web-based general-purpose bugtracker tool originally developed and used by the Mozilla project. Released as open source software by Netscape Communications in 1998, Bugzilla has been adopted by a variety of organizations for use as a defect tracker for both free software and proprietary products.

Bugzilla features:
•   Optimized database structure for increased performance and scalability
•   Excellent security to protect confidentiality
•   Advanced query tool that can remember your searches
•   Integrated email capabilities
•   Editable user profiles and comprehensive email preference
•   Comprehensive permissions system
•   Proven under fire as Mozilla's bug tracking system

HP OpenView

HP OpenView Service Desk gives enterprises and service providers a unique solution to successfully manage service levels. The integrated service desk functionality allows you to manage crucial support and service processes to successfully deal with today’s complex IT management challenges.

HP OpenView Service Desk helps you manage your service level agreements (SLAs) by showing you which IT elements your service is depending on, which customers are receiving the service, and who is managing and supporting the service. Now, with new levels of integration with HP OpenView Internet Services Manager and HP OpenView Service Navigator, HP OpenView Service Desk will allow your organization to manage your services better than ever before.

Features:
•   Demonstrates the relationships between customers, business services, servicelevel agreements and support level objectives;
•   Provides a hierarchical service structure with multi-tiered SLA capabilities;
•   Provides straightforward information in a recognizable format with an intuitiveMicrosoft Outlook look-and-feel user interface;
•   Offers the capability to customize forms, views and fields on the fly, withoutthe need to bring the application server down;
•   Provides out-of-the-box reporting capacities and database views to facilitatethe integration with external reporting tools.

BMC Remedy IT Service Management Suite

The BMC Remedy IT Service Management Suite reduces complexity and makes customer support, change management, and asset management integrated and efficient. With BMC, you can benefit from the following:
•   One suite of integrated applications means quicker implementation, accelerated learning curve, and lower TCO
•   One partner for industry-leading software, services, and training means you will fast-track your ITIL initiatives by up to 50 percent
•   One architecture that includes both the leading CMDB and the leading service desk
•   One clear leader in both CMDB and service desk market share

A complete list of help desk software products is present at </p>

http://www.opensourcehelpdesklist.com/