Zabbix - Track, record, alert and visualize performance and availability of IT resources
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.
Statista - The Statistics Portal for Market Data, Market Research and Market Studies
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.
Montecarlito - MonteCarlito is a free Excel-add-in to do Monte-Carlo-simulations.
Nagios - Complete monitoring and alerting for servers, switches, applications, and services