tiddlyspot lets you make your own online wiki.
You can also make it private if you want.
Superb. I was looking for exactly this. I first came across TiddlyWiki, which lets you download and customize an html file into your own personal single-file wiki. Fun, but I wanted something online.
tiddlyspot is based on TiddlyWiki, so you get the best of TiddlyWiki but then online.
Oh yeah, you can also download your tiddlyspot wiki locally of course...