TiddlyWiki
TiddlyWiki is written in HTML, CSS and JavaScript to run on any reasonably modern [[browser|Browsers]] without needing any ServerSide logic. It allows anyone to create personal SelfContained hypertext documents that can be published to a web server, sent by email, stored in a Dropbox or kept on a USB thumb drive to make a WikiOnAStick. Because it doesn't need to be installed and configured it makes a great GuerillaWiki.