- [Adagios](http://adagios.org/) - Web based Nagios interface for configuration and monitoring (replacement to the standard interface), and a REST interface. ([Source Code](https://github.com/opinkerfi/adagios)) `AGPL-3.0``Docker/Python`
- [Bloonix](https://bloonix-monitoring.org/) - Bloonix is a monitoring solution that helps businesses to ensure high availability and performance. ([Source Code](https://github.com/bloonix)) `GPL-3.0``Perl`
- [Performance Co-Pilot](http://pcp.io) - Lightweight, distributed system performance and analysis framework.
- [PHP Server Monitor](https://www.phpservermonitor.org/) - Open source tool to monitor your servers and websites. ([Source Code](https://github.com/phpservermon/phpservermon))
- [PhpSysInfo](https://phpsysinfo.github.io/phpsysinfo/) - A customizable PHP script that displays information about your system nicely. ([Source Code](https://github.com/phpsysinfo/phpsysinfo))
- [Prometheus](https://prometheus.io/) - Service monitoring system and time series database. ([Source Code](https://github.com/prometheus/prometheus)) `Apache-2.0``Go`
- [pyDash](https://k3oni.github.io/pydash/) - Small web-based monitoring dashboard for linux. ([Source Code](https://gitlab.com/k3oni/pydash))
- [Riemann](http://riemann.io/) - Flexible and fast events processor allowing complex events/metrics analysis. ([Source Code](https://github.com/riemann/riemann))
- [rtop](https://github.com/rapidloop/rtop) - an interactive, remote system monitoring tool based on SSH. ([Source Code](https://github.com/rapidloop/rtop))
- [tcollector](http://opentsdb.net/docs/build/html/user_guide/utilities/tcollector.html) - System statistic collection daemon written in Python for OpenTSDB
- [Telegraf](https://github.com/influxdata/telegraf) - The plugin-driven server agent for collecting & reporting metrics.
* Dashboards
- [Dashing](http://dashing.io/) - Ruby gem that allows for rapid statistical dashboard development. An all HTML5 approach allows for big screen displays in data centers or conference rooms.
- [Facette](http://facette.io) - Time series data visualization and graphing software written in Go.
- [Freeboard](https://github.com/Freeboard/freeboard) - A damn-sexy front-end real-time dashboard for the internet of things. Transforms raw JSON into delicious UI.
- [Ganglia](http://ganglia.sourceforge.net/) - High performance, scalable RRD based monitoring for grids and/or clusters of servers. Compatible with Graphite using a single collection process.
- [Grafana](http://grafana.org/) - A Graphite & InfluxDB Dashboard and Graph Editor.
- [RRDtool](http://oss.oetiker.ch/rrdtool/) - Industry standard, high performance data logging and graphing system for time series data.
* Storage
- [InfluxDB](https://influxdb.com/) - Distributed time series database with no external dependencies.
- [KairosDB](https://github.com/kairosdb/kairosdb) - Fast distributed scalable time series database, fork of OpenTSDB 1.x.
- [OpenTSDB](http://opentsdb.net/) - Store and server massive amounts of time series data without losing granularity.
- [Beats](https://www.elastic.co/beats/) - Single-purpose data shippers that send data from hundreds or thousands of machines and systems to Logstash or Elasticsearch. ([Source Code](https://github.com/elastic/beats)) `Apache-2.0`
- [Collectd](https://collectd.org/) - System statistics collection daemon. ([Source Code](https://github.com/collectd/collectd)) `MIT``C`
- [Diamond](https://github.com/python-diamond/Diamond) - Daemon that collects system metrics and publishes them to Graphite (and others). `MIT``Python`
- [Grafana](https://grafana.com/) - A Graphite & InfluxDB Dashboard and Graph Editor. ([Source Code](https://github.com/grafana/grafana)) `AGPL-3.0``Go`
- [RRDtool](https://oss.oetiker.ch/rrdtool/) - Industry standard, high performance data logging and graphing system for time series data. ([Source Code](https://github.com/oetiker/rrdtool-1.x)) `GPL-2.0``C`
- [Statsd](https://github.com/etsy/statsd/) - Daemon that listens for statistics like counters and timers, sent over UDP or TCP, and sends aggregates to one or more pluggable backend services. `Nodejs``MIT`
- [tcollector](http://opentsdb.net/docs/build/html/user_guide/utilities/tcollector.html) - Gathers data from local collectors and pushes the data to OpenTSDB. ([Source Code](https://github.com/OpenTSDB/tcollector/)) `LGPL-3.0/GPL-3.0``Python`
- [Telegraf](https://github.com/influxdata/telegraf) - Plugin-driven server agent for collecting, processing, aggregating, and writing metrics. `MIT``Go`
* [OpenWrt](https://openwrt.org/) - A Linux-based router featuring Mesh networking, IPS via snort and AQM among many other features. ([Source Code](https://git.openwrt.org/openwrt/openwrt.git)) `GPL-2.0``C`
* [OPNsense](https://opnsense.org/) - An open source FreeBSD-based firewall and router with traffic shaping, load balancing, and virtual private network capabilities. ([Source Code](https://github.com/opnsense)) `BSD-2-Clause``C``PHP`