WikiWikiWeb is the name of a Hypertext system implemented as an application on
top of the World Wide Web, which tries to make it fast, easy, and simple to contribute to existing content.
The following are some other Wiki's that exist. I have not been to them all and cannot vouch for their quality nor can I say which is appropriate for which audience. So please use your own judgement. I have filled in a comment where I could.
The above names can be used in InterWikiLinks