VMmanager - VMmanager is a QEMU/KVM server virtualization management software, which presents perfect tools for creating virtual machines, providing VPS services, and building cloud infrastructure.
Zabbix - Track, record, alert and visualize performance and availability of IT resources
SolusVM - Solus Virtual Manager (SolusVM) is a powerful GUI based VPS management system with full OpenVZ...
Datadog - See metrics from all of your apps, tools & services in one place with Datadog's cloud monitoring as a service solution. Try it for free.
Virtualizor - Virtualizor is a powerful web based VPS Control Panel.
Wireshark - Wireshark is a network protocol analyzer for Unix and Windows. It lets you capture and interactively browse the traffic running on a computer network.