First time I've heard about nagios was 3 years ago from someone called Nathan. He went on and on about that system, how it can monitor pretty much everything and being open source can be integrated with our products. At that time I had small company called neta systems group and integrated different open source products under private brands.
somehow I've left nagios unchecked . I think cause nathan mentioned that it is waaaay to complicated to install then some other system we used :-).
anyways no I'm in opengaming and nagios was brought up again. And this time I've installed a beta version and now it monitors abut 30 server and growing.
I've made some scripts for it and will post them here as well.