Monitoring
Hyperic
Hyperic monitors the health and well-being of operating systems, Virtual Machines, application servers, web servers, databases, messaging servers, authentication systems, and more, in your environment, or the cloud.
http://www.hyperic.com
Groundwork
Groundwork builds upon the open source Nagios framework to provide enterprise class monitoring and alerting for heterogeneous operating systems, application and hardware environments.
http://www.groundworkopensource.com/
Nagios
Nagios is a powerful monitoring system that enables organisations to identify and resolve IT infrastructure problems before they affect critical business processes.
http://www.nagios.org/