In looking for a self-hosted online notebook I've just settled on #TiddlyWiki. Fully self-contained*, remarkably feature rich, no database of any kind (!!!!) and it's been supported by its original author and a sizeable community since 2004.
But it's tough to get past the fact that the basic element is called a Tiddler. Not an Item, a Note, or an Article. A "Tiddler". God the British are silly sometimes.
* If you're hosting it on the web and you want changes to be saved to the server you do have a little bit of work to do, but it's pretty simple on most platforms.