http://runslikeclockwork.com/pages/monit_aggregator
A free hosted version of the open source monit-aggregator written by Matt Fawcett. Appears to be free with no node restriction.
https://github.com/mattfawcett/monit-aggregator
Source code of monit-aggregator by Matt Fawcett / runslikeclockwork.com. He offers a free hosted version at that site.
http://www.pagerduty.com/
Takes alerts from monitoring systems and sends emails, phone calls and SMS messages. Handles on-call schedules, escalation, acknowledgement, etc.
http://reductivelabs.com/trac/puppet/
Put simply, Puppet is a system for automating system administration tasks. It's a language to define services, nodes, dependencies, and so on. Then it handles the "realisation" or "execution" of those definitions across multiple platforms, etc.
http://www.linuxnetworkcare.com/
Linux Network Care are a specialist Linux server management company. They offer remote server administration, technical support, appliance management (cPanel, Plesk, etc) and so on.
http://rack-admins.com/
Rack Admins are a server admin company which appear to be based out of Ukraine. Their charges start from $30/hour for administration, $60/hour for consultancy.
http://www.tildeslash.com/monit/
monit is a utility for managing and monitoring, processes, files, directories and devices on a UNIX system. Monit conducts automatic maintenance and repair and can execute meaningful causal actions in error situations.
http://www.linuxforums.org/misc/using_top_more_efficiently.html
A guide on how to get the most of out the linux top utility. Includes a description of the column names, and other tips & tricks.