TiddlyWiki -- one-file Wiki implemented in JavaScript. Strong community; many different (and interesting) adaptations at http://tiddlywiki.com/
** Classic -- The original. More mature, has more useful plugins, and requires an additional JSON file stored in the same folder of your tiddlywiki when using Chrome or IE.
** TiddlyWiki5 -- TiddlyWiki rewritten from the ground up based on HTML5 standards in order to to be as future-proof as possible. Currently in beta, lacking many features of the original (using plugins)(3/4/2014).
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See PersonalWiki
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CategoryWikiImplementation