* [Adagios](http://adagios.org/) - Web based Nagios interface for configuration and monitoring (replacement to the standard interface), and a REST interface, [SourceCode](https://github.com/opinkerfi/adagios), [Documentation](https://github.com/opinkerfi/adagios/wiki))
* [Alerta](https://github.com/guardian/alerta) - Distributed, scaleable and flexible monitoring system.
* [Bloonix](https://bloonix.org) - Bloonix is a monitoring solution that helps businesses to ensure high availability and performance. `GPLv3``Perl`
* [Bosun](http://bosun.org/) - Monitoring and alerting system by Stack Exchange ([Source Code](https://github.com/bosun-monitor/bosun), [Documentation](http://bosun.org/quickstart.html)) `MIT``Go`
* [Cacti](http://www.cacti.net) - Web-based network monitoring and graphing tool.
* [Cabot](http://cabotapp.com/) - Monitoring and alerts, similar to PagerDuty.