nagios-notify is a template-based notify script for Nagios. The templates can be easily edited in a text editor. You can change templates without restarting Nagios. With advanced templates, you can send richtext (even images) over jabber if you use nagios-notify-jabber. It depends only on basic Unix utilities.
check_mysql_health is a plugin for the Shinken (Nagios) software that allows you to monitor a MySQL database. Among the list of metrics are time to login, index usage, bufferpool hit rate, query cache hit rate, slow queries, temp tables on disk, table cache hit rate, connected threads, and many more. Requirements are either a DBD::mysql Perl module or a MySQL client package.
Lilac is a configuration tool for Nagios 3. Its features include enhanced Nagios 3 time period support, multiple template inheritance, host templates able to contain services, dependencies, and escalations, an importer which can import existing Nagios configurations and import from a Fruity installation, an Exporter with Nagios process control, the ability backup existing configuration files, and an auto-discovery tool to quickly add your infrastructure into your Nagios installation.
Check_MK is a complex addon for Nagios/Icinga and consists of three subprojects. The check and inventory system Check_MK is a general purpose Nagios plugin for retrieving data. It adopts a new approach for collecting data and obsoletes NRPE, check_by_ssh, NSClient, and check_snmp. It features a significant reduction of CPU use on the Nagios host and automatic inventory of items to be checked, and is especially useful with larger Nagios installations. "MK Livestatus" gives immediate and fast access to live and historic Nagios status data. It's a supported backend for many addons including NagVis, NagiosBP, and Thruk. "Check_MK Multisite" is a feature complete replacement for the Nagios GUI, and uses MK Livestatus as a backend. It is very fast, and supports efficient distributed monitoring.
The Ninja project is an attempt to develop an alternative Nagios GUI with the aim of being the most useful Open Source Web front end for Nagios. It improves searching and filtering and scalability. It supports templates and skins for customizing appearance, and supports several databases. You can use the components of Ninja in combination with the CGI scripts of the original Nagios Web GUI or as replacements for them.
The Merlin project was initially started to create an easy way to set up distributed Nagios installations, allowing Nagios processes to exchange information directly as an alternative to the standard method using NSCA. It has also been extended with fault tolerance, the ability to store status information in a database, and other features. This allows Merlin to function as a backend for applications such as the Ninja project.
CoffeeSaint is a Java application that shows the status of Nagios (version 1 up to 3 and the newer XI) on a screen. It can, if there are no errors, display a Webcam feed. If an error status occurs, it can play a sound. One can configure it to display certain errors/warnings always on top. It is remotely configurable via a built-in Web interface.
OpMon is a network and system monitoring application based on Nagios with extended support for capacity planning, SLA, SLM, network discovery, service catalogs, report schedule, Davinci, a dashboard builder, and much more. OpMon provides a GUI for Nagios as well as full multi-language support. The license to use the opmon proprietary modules is free for 2 hosts and 20 services. OpMon comes with many open source applications like phplogcon, Nedi, ntop, nagtrap, OCSInventory, OTRS, and opcfg.