Nagios - Complete monitoring and alerting for servers, switches, applications, and services
Zabbix - Track, record, alert and visualize performance and availability of IT resources
Eureka - Eureka is a contact center and enterprise performance through speech analytics that immediately reveals insights from automated analysis of communications including calls, chat, email, texts, social media, surveys and more.
Linux Dash - A drop-in, low-overhead monitoring web dashboard for a Linux machine.
Netdata - Monitor your servers, containers, and applications, in high-resolution and in real-time.
Spiceworks Help Desk - Help desk software features that work for IT