Intelligent Platform Management Interface(IPMI) is a technology available on many modern servers that allows for remote or local access and control of a variety of server features. IPMI is implemented on a Baseboard Management Controller, which can normally be configured through BIOS and may have a dedicated NIC or use one of the systems existing NICs. In addition to hardware implementations on BMC device drivers for the OS kernel are necessary for host systems to access their own IPMI interfaces natively, on Linux OpenIPMI is a common tool.
While IPMI is a powerful tool it should be noted that there are some security concerns and the US Computer Emergency Readiness Team has issued the following statement about the use of IPMI. Before implementing IPMI for use on your local network make sure you have reviewed the security considerations and have taken appropriate precautions.
In addition to a number of command line tools available for IPMI there are several pieces of datacenter management software that can detect and manage devices with IPMI interfaces. Some of these programs include Nagios and Intel's Datacenter Manager. These and similar tools offer a graphical interface for managing large numbers of systems through their IPMI interfaces as well as access to systems with other types of management interfaces like SNMP.