In XP you could use DokuWikiStick (
http://www.splitbrain.org/blog/2008-05/16-dokuwiki_on_a_stick_2008-05-05). You don't have the hassle of installing any server. Just a doubleclick and your DokuWiki is running.
I guess that in Ubuntu, the very same directory can be used too, but I don't have any experience with it.