This is an idea that I have been thinking about for a year or so. When I first started studying wikis and especially science (and nanotechnology in particular) a couple of years ago, I came upon a wiki that had a sort of train or bus system within it, that ran from wiki to wiki. It may have been the Meatball Wiki.
My idea is to construct a Virtual railway among all of the Wikia wikis (at least among those Wikia wikis that are interested in joining the Virtual Railway system).
All that each Wikia wiki needs is interest in the project and to construct a page for the Virtual Railway to run through, a sort of Grand Central Station destination. The virtual railway would consist of links that connected all of the Wikia wikis together. There would be several rail lines. They would be color-coded Green, Blue, Red, Black, White, Gray and so on according to subject. Science Wikias could be reached using the Blue Line, for example. We would in effect be constructing a Virtual metropolitan subway system, connecting all of the Wikia wikis by train lines. I was thinking Black Line for Internet-related Wikias.
I'm thinking of stumping for assistance over at the Central Wikia, since that wiki amounts to a central marketplace for all 2300 Wikia.