I use quite a few monitoring tools, one for each "kind" of monitoring... -For server uptime, stats, etc I use nagios -For security monitoring, I mix the open

I use quite a few monitoring tools, one for each "kind" of monitoring... -For server uptime, stats, etc I use nagios -For security monitoring, I mix the open source OSSEC + Snort: http://www.ossec.net http://www.ossec.net -For availability+integrity remote monitoring of my sites/domains I use sucuri: http://sucuri.net http://sucuri.net