I'm trying to get a little for-fun Wiki going, but I just haven't been able to find software that fits the bill. I asked for suggestions in here a long time ago, but there really wasn't anything back then. Maybe things have changed since then...
All I really want is a very simple to install and use Wiki, but one that also provides some user security features--at the very least that lets me require a login with password to edit pages (my sites seem to be of the sort that attract extremely annoying and malicious people, so this ability is an absolute must). Not pounding on the DH server if it ever gets popular would be a nice bonus.
DH's Perl module "insta-wiki" was almost perfect in terms of simplicity, but has no user authentication features. Tiki seems to be popular, but looks suspiciously like massive overkill since it has a mess of CMS stuff I don't want. PHPWiki looks like it might fit the bill, but last time I tried it I couldn't get the user authentication features to work (are they working now?). I've heard that Twiki is slow, and it looks like overkill.