Personal wiki in a single file

For about a year I am using TiddlyWiki. Jeremy Ruston created a great wiki system based on a single HTML file. It heavily uses java script.

Another great thing in TiddlyWiki is that you can change CSS, add macros, add and change content in the same way. You just write or edit "tiddlers". Tiddler may include text notes or macro or CSS. It is pretty easy and comfortable