I use Nagios to monitor a few clients’ servers (and my own) and I have written a number of plugins for special purposes. Here’s a list of some of the plugins that I have written and which have an open-source license. Those which don’t have a link to their own pages can be made available upon request, or they will eventually be made available here when I find the time to write proper documentation.

• check_svnstatus – checks a subversion working copy for modifications
• check_tsusers – checks the number of user sessions on a Windows Terminal Server, divided into inactive sessions, active sessions, and total sessions

The plugins should work just fine with other monitoring software that uses Nagios compatible plugins, e.g. Icinga, but I have never tested this myself.