DiamanteDesk - DiamanteDesk is an open-source easy-to-use help-desk solution.
Zabbix - Track, record, alert and visualize performance and availability of IT resources
Zendesk - Zendesk is a beautiful, lightweight help-desk solution.
openITCOCKPIT - openITCOCKPIT is a leading open source monitoring framework based on Naemon (Nagios). In addition it integrates Checkmk and Prometheus. It also offers interfaces to Icinga2, PRTG and opManager to obtain status and performance from them.
Nagios - Complete monitoring and alerting for servers, switches, applications, and services
OTRS ITSM - OTRS ITSM is a fundamental solution for IT Service Management organizations.