Munin is a system to gather and graph all sorts of
information. You can install a node on the various
machines in your network, as well as on a central
server. The nodes will know how to extract various
kinds of information, such as load average and
bandwidth usage, and will wait for the server to
request these values. The output is in HTML
format. The server can optionally send notifications if
any of the values move outside of a specified
range (and when they move back into it).
