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Have you looked at TiddlyWiki? http://tiddlywiki.com/

It's a simple wiki-on-a-page, with collapsing and linking built in. You can also keep it completely off-line, or have it sync with your preferred solution (Dropbox in my case).

I absolutely must have control over my own notes. The primary reason I'm using org-mode + dropbox is that I can replace that system with some other file-sync on my own if dropbox goes away.

Well, it'd be nice (well, actually, quite necessary) for it to be available offline.