Nelmon is a collection of plugins for Nagios and compatible products
A wireshark dissector plugin for the IEEE 1905.1 protocol.
Acquires external IP address from command line
Nagios plugins for checking voltage readings
...has moved to packetpeeper.org
FAN is Linux-based operating system provided Nagios
Graylog2 Server Appliance for Windows
Network Intrusion Detection and Full Packet Capture System
GLPI plugin to import GLPI connected host into Zabbix
Some Plugins for Nagios and Icinga