If anyone finds that thread, please send a link for posting at http://wikiindex.org or just go post it there yourself. Thanks!
Thanks to Google, I've been able to find (or re-discover) the site I had in mind. I don't remember how I got to it in the first place (apparently it wasn't the thread mentioned before), but I don't think that matters too much.
It's called Enterprise Wikimania and is hosted by Socialtext: http://www.eu.socialtext.net/ewikimania/index.cgi I can't say anything about its contents though because I haven't taken a closer look at it yet.
Therefore, I would also prefer if someone more knowledgeable would add it to WikiIndex.
HTH.
-- F.