I've tried many packages, have settled on Nagios + Cacti. Featureful, rock solid, free, scales well, documentation galore. How can you beat that? A live example -- Wikipedia uses Nagios for their monitoring solution: http://nagios.wikimedia.org/nagios/cgi-bin/status.cgi?host=a... , they monitor more than 2,000 services on 426 hosts. At my college, Nagios has an icon for each host that links to a corresponding wiki page.