PRTG Network Monitor!

An uncompromising mature enterprise-level platform designed for real-time monitoring of millions of metrics collected from tens of thousands of servers, virtual machines and network devices, effortlessly scaling to even larger environments.

Join millions of IT professionals and download Spiceworks, a free network monitoring software with network management tools, help desk ticketing app, network mapper and more.

LibreNMS is an autodiscovering PHP/MySQL based network monitoring system forked from Observium. LibreNMS aims to be easy to use, painless to deploy, and support monitoring of a wide range of devices. Observium's license changed to a modified QPL license in May 2012, and recently was split into free and commercial versions. Our aim with LibreNMS is to continue to create a usable NMS, but with a community focus and GPL licensing.

Munin is a networked resource monitoring tool that can help analyze resource trends and "what just happened to kill our performance?" problems. It is designed to be very plug and play. A default installation provides a lot of graphs with almost no work.

NetSpeedMonitor is a lightweight Network Monitoring Toolbar for your Windows Taskbar designed to be used on computers that run Windows XP, Windows Server 2003, Windows Vista or Windows 7. With NetSpeedMonitor you can monitor the current speed (up- and downstream) of your Network Interfaces and the amount of data transferred. In addition to the Connection Table with all TCP/UDP endpoints and the Toolbar Tooltip with a quick and short traffic overview, you can also see detailed daily and monthly Traffic Statistics. NetSpeedMonitor toolbar requires no additional drivers like other Network Monitoring tools do! »

Datadog is a monitoring service for IT, Dev & Ops teams who write and run applications at scale, and want to turn the massive amounts of data produced by their apps, tools and services into a unified view of IT infrastructure. Datadog's capabilities are provided on a SaaS-based data analytics platform that enables multiple teams to work collaboratively on infrastructure issues.

netdata is a system for distributed real-time performance and health monitoring. It provides unparalleled insights, in real-time, of everything happening on the system it runs (including applications such as web and database servers), using modern interactive web dashboards.

CurrPorts is network monitoring software that displays the list of all currently opened TCP/IP and UDP ports on your local computer. For each port in the list, information about the process that opened the port is also displayed, including the process name, full path of the process, version information of the process (product name, file description, and so on), the time that the process was created, and the user that created it.

DU Meter is a network bandwidth monitor for your computer. It shows real-time graphs and can create reports and alerts based on your downloads and uploads. It enables you to use your internet connection more efficiently by providing an accurate visualization of the data that flows through your computer's network connection.

BitMeter OS keeps track of how much you use your internet/network connection, and allows you to view this information in a variety of ways.

Cabot is a free, open-source, self-hosted infrastructure monitoring platform that provides some of the best features of PagerDuty, Server Density, Pingdom and Nagios without their cost and complexity.

Pandora FMS is an enterprise-ready monitoring solution that provides unparalleled flexibility for IT to address both immediate and unforeseen operational issues, including infrastructure and IT processes. It uniquely enables business and IT to adapt to changing needs through a flexible and rapid approach to IT and business deployment.

Observium is an autodiscovering PHP/MySQL/SNMP based network monitoring which includes support for a wide range of network hardware and operating systems including Cisco, Linux, FreeBSD, Juniper, Brocade, Foundry, HP and many more.