MediaWiki is actually pretty easy to set up on a web server, speaking as someone who's now done it twice. You plop the files into htdocs, make sure PHP is set up, set up vanity URLs if you want to, and then… well, that's it. The final step is to go to the site, fill in the setup form, download the settings file it gives you and upload it. It doesn't even need an external database, it can use SQLite; if email setup is annoying, it doesn't even need that. And it's the most powerful and flexible wiki software out there: if there's something you want a wiki to do, MediaWiki can do it, but it also isn't too bloated out of the box, so you can just install plugins as and when you need them. Thoroughly recommend it.