How do you best configure Ganglia to work with MonAMI? What's a good Nagios configuration? MonAMI is designed to fit in with existing monitoring tools; but, sometimes those external tools need to be tweaked to get the best out of the available data.
External is a collection of scripts, configuration hints, and similar "useful stuff". It's material not for MonAMI, but rather for the programs MonAMI communicates with (hence "external").
The current focus has been on getting decent graphs within Ganglia. External has a framework for building RRDTool graphs, pie charts, and frames of related information. It also includes a fair number of examples showing how to use the framework. The torque and maui frames are excellent examples: see the output from UKI-SCOTGRID-Glasgow.
For now, external is available as a CVS module (browse, instructions).