This is a list of the best and most interesting 3rd party plugins, several of which I have used or come across over the years that deserve mention, usually due to their better quality than the typical Nagios Exchange / Icinga Exchange plugins.
- check_openmanage - Dell OpenManage Hardware monitoring plugin by Trond Hasle Amundsen
- check_drbd - can't remember if this is the plugin I used to use but I used to love it telling me when DRBD was behind by how much and caught up
- check_tsd - OpenTSDB metrics query
- check_prometheus_metric.sh - I don't normally bash scripts as Nagios Plugins but this is in the official project so is worth a look
- collectd-nagios - queries Collectd metrics for Nagios alerting
- collectd exec-nagios.px - executes a Nagios Plugin and returns the metric to Collectd to forward on to one of the many compatible metrics graphite solutions