TiddlyWiki is an extremely portable Wiki that is easy to install. You download a single file and place it into the directory where you want to access it. You can load it onto a USB drive, a Web server, your desktop, pretty much anywhere.

I've installed it in two places to try it out. First, I put an instance on my iMac. It has been easy to update and load posts to. The second was on my web domain. I've found updating it on my web server is tougher. For the life of me, I can't figure out how to set it up to allow me to write to it.