The Wikipedia is an "open source" encyclopedia available free to anyone and--and this is the crucial, mysterious part--written and edited by anyone, too. So far it's accumulated 300,000+ articles on topics ranging from astronomy to zoology.
It shouldn't work, really. Anyone who's ever participated in a group writing effort knows what a frustrating, soul-sucking exercise it can be. And of course the more scriptwriters a movie has, the worse it usually is. And yet, judging by my random walk through it, the Wikipedia has accumulated an immense amount of high-quality content.
Two questions arise: 1) where does the labor come from? And 2) what keeps the result from being a seething mass of contradictory gobbledygook? To the first question, I've always felt that open source efforts harness "hobby time" (and often-powerful hobby passions) that might otherwise be spent on model railways or antique collectibles. For people whose hobby is writing English (as opposed to C++), the Wikipedia is a natural and attractive outlet by which to showcase their skills. To the second question, I don't have a good answer. Disputes among the 200 or so regular contributors (to the English language version) apparently occur, but there's a well-specified mediation/arbitration process. Perhaps the secret is that such "collisions" are actually rather rare: human knowledge is vast and it's probably easy to stake out territory that few are interested in. If that's the case, then there's little for other group writing efforts--encyclopedias, dictionaries and other wide-ranging reference works may be uniquely well-suited to the Wikipedia's approach. Alas.--Ed Gottsman