Millennium Village was a pavilion set up for the Millennium Celebration at EPCOT. It essentially showcased many countries that were not present in World Showcase. It was between the UK and Canda I believe.
On a side note, I think World Showcase would have been much better suited for it's own independence. A park like that is rumored to be appearing in Florida soon.
There are also long-running rumours that the third park in Paris (if we ever get that far) will be a variation on the World Showcase theme, but built more on a Magic Kingdom model, with different geographical "lands", rather than strictly deliniated pavillions. (For example, look at the differences between the representation of Italy in EPCOT and Tokyo DisneySea.)
Ah, maybe one day...
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Re: A World Showcase Never Built...
Never heard that one but it could be cool. With so many Eurpeans visitng DLP (No way, really?) they'd have to shoot for more South American and Asian and North American feels (to actually be exotic) which means potential for new things to be cloned to WS.