The MultiMachine wiki will attempt to describe both the physical piece of home-built machining equipment, and the project that spawned it.
The machine has two different major formats: The engine block multimachine and the concrete multimachine. Both machines are, broadly speaking, a heavy-duty horizontal milling machine with features to act as a very versatile lathe. The original version of this machine (and currently the only version that has been physically implemented) was Pat Delany's machine, based on a small horizontal milling machine that George Ewen built and wrote a magazine article about. Subsequently, Costas built one in Greece. I'm not sure who else has ever built one, but when I find out, I'll put the list at list of multimachines in the wild…
Since that time, the design has evolved towards a larger machine, built around a concrete casting. This version may have round bar ways, or prismatic ways… Jeremy is building one in Africa some place. The concrete casting for machine tools idea was developed by Lucien I. Yeomans, and documented extensively by Pat Delany's vision of a machine tool that could be built by people in very economically depressed areas, and that could be used to start new businesses repairing machines and equipment necessary for survival.
This project breaks into a bunch of aspects beyond the nuts and bolts of building a multimachine.
There is a bunch of information regarding efforts that have been made to contact NGO's and other people who could influence the adoption of this technology.
There is an attempt to collect documentation. This breaks down into materials to educate new users, resurrection of old, lost technologies, and other collected free documentation that might be of use to people who build the machine.