Wiki have been around since 1995 but have attracted increased interest recently, perhaps owing to the new-found interest in social software. Frankly it's a new term for me but it feels good to know about web sites written entirely by its users (a Groupware?). Yes, that means — open editing, anyone can edit the site contents (even delete material). That lets me wonder on the version controlling the site moderators need to perform, enormous. Wiki does not invlove fancy graphis, layout, it's pure simple HTML. This makes me wonder too: when blogs of today are getting more and more colorful and flashy what drives people towards a non WYSIWYG medium again.
BTW, Wiki Wiki is Hawaiian for “Quick.”