Re: Extranet Setup?
Of course, Cep, most of the tikis have an extranet part (at least) on their sites. Intranet or extranet depend on the permissions that you grant to the anonymous users (without login and password). Maybe you need to read about users and groups management, permissions, etc. (search doc.tw.o or tw.o for this issue).
And have a look at: http://tikiwiki.org/TikiSitesBestOf , for instance, or any of the other Tiki sites.
Last, ask again if you still have questions about it...
Hope this helps,