WhoISP

Tech Support SW
Defect Tracking System - From the folks that brought you Radiator. (Commercial)
Faq-O-Matic - The Faq-O-Matic is a CGI-based system that automates the process of maintaining a FAQ (or Frequently Asked Questions list). A permission system also makes it useful as a help-desk application, bug-tracking database, or documentation system.
Inovaware Resolve - Resolve is a sophisticated Help Desk and Knowledge Base that leverages the Synchronized Business Infrastructure to help you streamline support, improve productivity and reduce the costs associated with traditional call centers.
Open Directory Help Desk software list
Wonder Desk - Wonderdesk is a fully automated help desk CGI script. (Commercial)