Support Incident Tracker (or SiT!) is a Free Software/Open Source (GPL)
web based application which uses PHP and MySQL for tracking technical support
calls/emails (also commonly known as a 'Help Desk' or 'Support Ticket System').
Manage contacts, sites, technical support contracts and support incidents in
one place. Send emails directly from SiT!, attach files and record every
communication in the incident log. SiT is aware of Service Level Agreements and
incidents are flagged if they stray outside of them.

WWW: http://sitracker.org