Check_MK!

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.

Icinga is a fork of Nagios and is backward compatible. So, Nagios configurations, plugins and addons can all be used with Icinga. Though Icinga retains all the existing features of its predecessor, it builds on them to add many long awaited patches and features requested by the user community. Icinga is an enterprise grade open source monitoring system which keeps watch over a network and any conceivable network resource, notifies the user of errors and recoveries, and generates performance data for reporting. Scalable and extensible, Icinga can monitor complex, large environments across dispersed locations. Icinga is licensed under GPL V2. »

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.

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.

OpenNMS is an enterprise grade network monitoring and network management platform developed under the free software or open source model. It consists of a community-supported, free-software project as well as an organization offering commercial services, training and support.

Shinken is an open source computer system and network monitoring software application compatible with Nagios. It's written in Python and therefore is able to run on all platforms where a Python interpreter is available.In contrast to Nagios it is not a monolithic system. Shinken runs as a bunch of highly specialized processes, avoiding the bottlenecks of a single-process design. This parallelity allows to run Shinken not only on one single server. It's components can be distributed over a whole server farm, which results in incredible scalability.Shinken is actively developed and already got more features than Nagios (like priorities for objects, business processes, auto-generation of services, discovery,...) »

Zenoss (Zenoss Core) is an open source application, server and network management platform based on the Zope application server. Released under the GNU General Public License (GPL) version 2, Zenoss Core provides a web interface that allows system administrators to monitor availability, inventory/configuration, performance and events.

Opsview Atom is ideal for personal use, SoHo setups, test or lab environments or just to get your hands dirty with all of Opsview's monitoring functionality!

Opsview is award winning unified service monitoring software for complex, distributed IT infrastructures.

The Sensu Open Source Project (a.k.a. "Sensu Core") intends to provide an open framework for building comprehensive monitoring solutions, without imposing restrictions or being overly opinionated. While new user-facing "features" may be developed exclusively in Sensu Enterprise, the framework that makes those features possible will always be a part of Sensu Core.

Centreon is a GUI built ontop of Nagios.

Server and application performance monitoring has never been easier or more affordable. With agentless monitoring for hundreds of applications and hardware types, Server & Application Monitor delivers the management, alerting, and reporting you need to keep your servers and apps running at peak performance. Top 5 reasons to choose SolarWinds over SCOM: 1. Agentless monitoring provides quick comprehensive coverage and low overhead.2. Functional dashboards and common sense navigation are standard in SolarWinds SAM.3. Breadth of platform coverage, single pane of glass for server, application, network and storage health, extensible monitoring framework for custom applications.4. Affordable pricing. No professional services needed.5. Frequent functional updates. SolarWinds provides functional releases 2X per year »

IT monitoring has never been easier - lean back and let CloudRadar keep an eye on your servers, services and hosts. Up and running in minutes. No back doors.