OTRS is an Open source Ticket Request System (also well known as trouble ticket system) with many features to manage customer telephone calls and e-mails. (GPL)

RT is an enterprise-grade ticketing system which enables a group of people to intelligently and efficiently manage tasks, issues, and requests submitted by a community of users. (GPL)

Tracmor is an on-demand solution for tracking your assets and inventory. Tracmor is easy to use and can be accessed from anywhere with an internet connection. (ZPL)